Etymology dictionary
incondite (adj.) — indelicate (adj.)
incondite (adj.)
1630s, "ill-made," earlier "crude, upolished" (1530s), from Latin inconditus "disordered, uncouth," from in- "not, opposite of" (see in- (1)) + conditus, past participle of condere "put together," from assimilated form of com- "together" (see com-) + -dere "put," from PIE root *dhe- "to put, place." Applied from 1845 to natural utterances ("oh!") from Latin (vox) incondita.
inconducive (adj.)
1729, from in- (1) "not, opposite of" + conducive.
incongruent (adj.)
mid-15c., from Late Latin incongruentem (nominative incongruens), from in- "not" (see in- (1)) + congruens (see congruent). Related: Incongruently.
incongruence (n.)
c. 1600, from Late Latin incongruentia "incongruity," from incongruentem (nominative incongruens) "incongruous, inconsistent," from in- "not" (see in- (1)) + congruens (see congruent). Related: Incongruency.
incongruous (adj.)
1610s, from Latin incongruus "incongruous, inconsistent," from in- "not, opposite of, without" (see in- (1)) + congruus "fit, suitable" (see congruent). Related: Incongruously; incongruousness.
incongruity (n.)
1530s, "quality of being incongruent," from French incongruité (16c.) or directly from Medieval Latin incongruitas, from Latin in- "not" (see in- (1)) + congruitas (see congruity). Meaning "that which is incongruent, an example of incongruency" is from c. 1600.
inconsequence (n.)
1580s, from Late Latin inconsequentia, from Latin inconsequens "inconsequent" (see inconsequent).
inconsequent (adj.)
1570s, "not following as a logical conclusion," from Latin inconsequentem (nominative inconsequens) "not logically connected, not resulting from what has preceded," from in- "not, opposite of, without" (see in- (1)) + consequens, past participle of consequi "to follow" (see consequence). Related: Inconsequently.
inconsequential (adj.)
1620s, "characterized by inconsequence;" 1782, "not worth noticing;" see inconsequent + -al (1). Related: Inconsequentially.
inconsiderate (adj.)
late 15c., "done thoughtlessly, heedless, careless, indiscreet," from Latin inconsideratus "headstrong, unadvised," of persons, "thoughtless," literally "not properly considered," from in- "not, opposite of" (see in- (1)) + consideratus (see consider). Sense of "without regard for the feelings of others" is from 1842. Related: Inconsiderately.
inconsiderateness (n.)
1590s, "imprudence," from inconsiderate + -ness. From 1858 as "want of consideration for others."
inconsiderable (adj.)
1590s, "incalculable;" from 1630s as "not worthy of consideration or notice," from French inconsidérable (16c.), from in- "not" (see in- (1)) + considérable (see considerable). Related: Inconsiderably. OED has found an instance of the rare verb inconsider from 1697.
inconsideration (n.)
1520s, "indiscretion, rashness, failure to consider," from Late Latin inconsiderationem (nominative inconsideratio) "inconsiderateness," from Latin inconsideratus "headstrong, thoughtless" (see inconsiderate).
inconsistency (n.)
1640s, "something which is inconsistent;" 1650s as "quality of being inconsistent," from in- (1) "not, opposite of" + consistency. Related: Inconsistencies. Inconsistence (1630s) is marked "Now rare or Obs." in OED.
inconsistent (adj.)
1640s, "not agreeing in substance or form;" 1650s, "self-contradictory," from in- (1) "not, opposite of" + consistent. Related: Inconsistently.
inconsolable (adj.)
1590s, from Latin inconsolabilis "inconsolable," from in- "not" (see in- (1)) + consolabilis "consolable," from consolari (see console (v.)). Related: Inconsolably (c. 1500).
inconspicuous (adj.)
1620s, "invisible," from Late Latin inconspicuus "not conspicuous," from in- "not, opposite of, without" (see in- (1)) + Latin conspicuus (see conspicuous). Weakened sense of "not readily seen or noticed" developed by 1828. Related: Inconspicuously; inconspicuousness.
inconstant (adj.)
c. 1400, "fickle, not steadfast," from Old French inconstant "variable, eccentric" (14c.), from Latin inconstantem (nominative inconstans) "changeable, fickle, capricious," from in- "not, opposite of, without" (see in- (1)) + constantem (see constant). Related: Inconstantly.
inconstance (n.)
late 14c., inconstaunce, "changeableness in action, feeling, etc.; fickleness, unsteadiness," from Old French inconstance "inconstancy, instability" (13c.) and directly from Latin inconstantia "inconstancy, fickleness," abstract noun from inconstans "changeable, inconsistent" (see inconstant). In English, inconstancy is now the usual word.
inconstancy (n.)
1520s, of persons, "fickleness;" 1610s, of things, "mutability, irregularity," from Latin inconstantia "inconstancy, fickleness," abstract noun from inconstans "changeable, inconsistent" (see inconstant).
inconsumable (adj.)
"incapable of being consumed," in any sense of that work, 1640s in reference to fire; 1785 in political economy; from in- (1) "not" + consumable. Inconsumptible is from 1570s.
inconsummate (adj.)
"unfinished, incomplete," 1640s, from Late Latin inconsummatus "unfinished," from in- "not" (see in- (1) + consummatus "perfected, complete," past participle of consummare "sum up, to complete" (see consummation).
incontestable (adj.)
"not admitting of dispute or debate, too clear to be controverted," 1670s, from in- "not" (see in- (1)) + contestable (see contest (v.)). Perhaps from or modeled on French incontestable. Related: Incontestably.
incontiguous (adj.)
"not adjoining or touching, separate," 1650s, from Late Latin incontiguus, from in- "not" (see in- (1)) + contiguus (see contiguous). Related: Incontiguously; incontiguousness.
incontinently (adv.)
early 15c., "immediately, without delay, at once," from incontinent + -ly (2). From 1550s as "unchastely;" in reference to bodily discharges from 1847.
incontinence (n.)
late 14c., "inability to restrain sexual desire, sexual immorality," later "inability to keep to a religious rule" (early 15c.), from Old French incontinence "lack of abstinence, unchastity" (12c.) or directly from Latin incontinentia "greediness; incontinence, inability to contain," abstract noun from incontinens "incontinent, immoderate, intemperate" (see incontinent). Meaning "inability to restrain bodily functions" is from 1754.
incontinency (n.)
early 15c., "unchastity;" see incontinent + abstract noun suffix -cy.
incontinent (adj.)
late 14c., "wanting self-restraint," from Old French incontinent (14c.) or directly from Latin incontinentem (nominative incontinens) "immoderate, intemperate, not holding back," from in- "not, opposite of" (see in- (1)) + continens (see continent (adj.)).
Originally chiefly of sexual appetites. General sense of "unable to retain" is from 1640s; medical sense of "unable to control bowels or bladder, unable to restrain natural discharges from the body" is attested by 1828.
incontrovertible (adj.)
"too clear or certain to admit of dispute or controversy," 1640s, from in- (1) "not" + controvertible (see controvert). Related: Incontrovertibly; incontrovertibility.
inconveniency (n.)
early 15c., "calamity, injury, harmful consequence," also "danger" (now obsolete), from Late Latin inconvenientia (see inconvenience (n.)). Meaning "trouble, disadvantage, quality of being inconvenient" is from 1550s.
inconvenient (adj.)
late 14c., "injurious, dangerous," also "absurd, illogical" (senses now obsolete), from Latin inconvenientem (nominative inconveniens) "unsuitable, not accordant, dissimilar," from in- "not, opposite of" (see in- (1)) + convenientem (see convenient). In early 15c., "inappropriate, unbecoming, unnatural;" also, of an accused person, "unlikely as a culprit, innocent." Sense of "troublesome, incommodious, awkward" is recorded from 1650s.
inconvenience (n.)
c. 1400, "harm, damage; danger; misfortune, affliction," from Old French inconvenience "misfortune, calamity; impropriety" (Modern French inconvenance), from Late Latin inconvenientia "lack of consistency, incongruity" (in Medieval Latin "misfortune, affliction"), abstract noun from inconvenientem (see inconvenient). Sense of "impropriety, unfitness; an improper act or utterance" in English is from early 15c. Meaning "quality of being inconvenient" is from 1650s.
inconvenience (v.)
"to give trouble, impede, or hamper" (someone), 1650s, from inconvenience (n.). Related: Inconvenienced; inconveniencing.
inconveniently (adv.)
mid-15c., inconvenientli, "wrongfully," from inconvenient + -ly (2). Meaning "with trouble or discomfort" is from 1650s.
inconvertible (adj.)
"incapable of being converted into or exchanged for something else," 1640s, from in- (1) "not, opposite of" + convertible (adj.). Related: Inconvertibly; inconvertibility.
incorporation (n.)
late 14c., incorporacioun, "act or process of combining substances; absorption of light or moisture," from Old French incorporacion or directly from Late Latin incorporationem (nominative incorporatio) "an embodying, embodiment," noun of action from past-participle stem of incorporare "unite into one body" (see incorporate (v.)). Meaning "the formation of a corporate body (such as a guild) by the union of persons, forming an artificial person," is from early 15c.
incorporate (v.)
late 14c., "to put (something) into the body or substance of (something else), blend; absorb, eat," also "solidify, harden," often in medical writing, from Late Latin incorporatus, past participle of incorporare "unite into one body, embody, include," from Latin in- "into, in, on, upon" (from PIE root *en "in") + verb from corpus (genitive corporis) "body" (from PIE root *kwrep- "body, form, appearance").
Meaning "to legally form a body politic with perpetual succession and power to act as one person, establish as a legal corporation" is from mid-15c. (A verb corporate was used in this sense from early 15c.) Intransitive sense of "unite with another body so as to become part of it" is from 1590s. Related: Incorporated; incorporating.
incorporeal (adj.)
early 15c., "spiritual, immaterial," with -al (1) and Late Latin incorporeus "without body," from in- "not" (see in- (1)) + adjective from corpus (genitive corporis) "body" (from PIE root *kwrep- "body, form, appearance"). The Old French adjective was incorporel. Glossed in Old English as lichhaemleas (see lich).
incorrect (adj.)
early 15c., "uncorrected, not chastened into obedience," of sinners, etc. (a sense now obsolete), from Latin incorrectus "uncorrected, not revised," from in- "not" (see in- (1)) + correctus, past participle of corrigere "to put straight; to reform" (see correct (v.)). Sense of "not in good style" is from 1670s; that of "factually wrong, erroneous, inaccurate" is from 1750s (implied in incorrectly).
incorrigible (adj.)
mid-14c., "incurable (of diseases, venom, etc.); extravagant (of expense); implacable (of hearts)," from Old French incorrigible "perfect, beyond rebuke or discipline" (14c.) or directly from Latin incorrigibilis "not to be corrected," from in- "not, opposite of" (see in- (1)) + corrigibilis, from corrigere "to correct," from com-, intensive prefix (see com-), + regere "to lead straight, rule" (from PIE root *reg- "move in a straight line," with derivatives meaning "to direct in a straight line," thus "to lead, rule"). From mid-15c. as "incapable of improvement" (of persons). Related: Incorrigibly. As a noun, from 1746.
incorrigibility (n.)
"incapability of correction or amendment," late 15c., incorrigibilite, from Medieval Latin incorrigibilitas; see incorrigible + -ity.
incorruptible (adj.)
mid-14c., of matter, "imperishable;" of the soul, etc., "immortal, everlasting," from Old French incorruptible (14c.), or directly from Late Latin incorruptibilis "incorruptible," from Latin incorruptus "unspoiled, unseduced," from in- "not" (see in- (1)) + corruptus, past participle of corrumpere "to destroy; spoil," figuratively "corrupt, seduce, bribe" (see corrupt (adj.)). From 1660s in English as "not corruptible morally," especially with reference to taking bribes, etc. Related: Incorruptibly.
incorruptibility (n.)
mid-15c., incorruptibilite, "quality of being imperishable," from Late Latin incorruptibilitas, from incorruptibilis (see incorruptible).
in-country (n.)
"interior regions" of a land, 1560s, from in (prep.) + country.
increase (n.)
late 14c., "action of increasing; results of an increasing," from increase (v.) or from verbs formed from the noun in Old French or Anglo-French. The stress shifted from 18c. to distinguish it from the verb.
increase (v.)
mid-14c., encresen, "become greater in size or number" (intransitive); late 14c., "cause to grow, enlarge" (transitive), from Anglo-French encress-, Old French encreiss-, present participle stem of encreistre, from Latin increscere "to increase, to grow upon, grow over, swell, grow into," from in- "in" (from PIE root *en "in") + crescere "to grow" (from PIE root *ker- (2) "to grow"). Modern English restored the Latin spelling 16c. Related: Increased; increasing.
increasingly (adv.)
late 14c., from increasing (see increase (v.)) + -ly (2).
incredible (adj.)
early 15c., "unbelievable, surpassing belief as to what is possible," from Latin incredibilis "not to be believed, extraordinary," from in- "not" (see in- (1)) + credibilis "worthy of belief" (see credible). Used c. 1400 in a now-extinct sense of "unbelieving, incredulous." Related: Incredibly; incredibility.
incredulity (n.)
"disbelieving frame of mind," early 15c., incredulite, from Old French incrédulité, from Latin incredulitatem (nominative incredulitas) "unbelief," noun of quality from incredulus "unbelieving" (see incredulous).
incredulous (adj.)
"unbelieving," 1570s, from Latin incredulus "unbelieving, incredulous," from in- "not" (see in- (1)) + credulus "that easily believes, trustful" (see credulous). Formerly also of religious beliefs. Related: Incredulously; incredulousness.
incremental (adj.)
1715, from increment + -al (1). Related: Incrementally.
increment (n.)
mid-15c., "act or process of increasing," from Latin incrementum "growth, increase; an addition," from stem of increscere "to grow in or upon" (see increase (v.)). Meaning "amount of increase" first attested 1630s.
increpation (n.)
"a chiding, a rebuking, censure," c. 1500, from Late Latin increpationem (nominative increpatio), noun of action from past participle stem of Latin increpare "to make noise at, scold, nag, upbraid," from in- "in" (from PIE root *en "in") + crepare "to creak" (see raven (n.)).
incrimination (n.)
"act or fact of charging with a crime." 1650s, noun of action from Medieval Latin incriminare "to incriminate, accuse," from in- "in" (from PIE root *en "in") + criminare "to accuse of a crime," from crimen (genitive criminis) "crime" (see crime).
incriminate (v.)
"charge with a crime, accuse," 1730, a back-formation from incrimination (q.v.) or else from Medieval Latin incriminatus, past participle of incriminare "to incriminate, accuse." Related: Incriminated; incriminating.
incriminatory (adj.)
"tending to incriminate, accusatory," 1838; see incriminate + -ory.
incroyable (n.)
1796, a name for the French fop or dandy of the period of the Directory (1795-1799), from French incroyable, literally "incredible" (15c.), from in- "not, opposite of, without" (see in- (1)) + croire "to believe," from Latin credere "to believe" (see credo). Said to be so called from their extravagant dress, and also, according to OED, from a favorite expression among them ("C'est vraiment incroyable").
incrustation (n.)
in early use also also encrustation, "act of covering or lining with a foreign substance; state of being incrusted," 1640s, from French encrustation, incrustation, from encruster (see encrust). Or perhaps from the obsolete English verb incrustate, which is attested from 1560s.
incus (n.)
middle ear bone, 1660s, from Latin incus "anvil," from incudere "to forge with a hammer," from in- "in" + cudere "to strike, beat," from PIE *kau-do-, suffixed form of root *kau- "to hew, strike" (see hew). The bone so called by Belgian anatomist Andreas Vesalius (1514-1564).
incubation (n.)
1610s, "a brooding," from Latin incubationem (nominative incubatio) "a laying upon eggs," noun of action from past participle stem of incubare "to hatch," literally "to lie on, rest on," from in- "on" (from PIE root *en "in") + cubare "to lie" (see cubicle). The literal sense of "sitting on eggs to hatch them" in English is first recorded 1640s.
incubator (n.)
"apparatus for hatching eggs by artificial heat," 1845, agent noun from incubate (v.). Late Latin incubator meant "one who lies in a place."
incubate (v.)
1640s (transitive), "to brood upon, watch jealously" (figurative); 1721 in literal sense "to sit on (eggs) to hatch them," from Latin incubatus, past participle of incubare "to lie in or upon," also in the figurative sense "brood" (see incubation). Intransitive sense "to sit upon eggs" is from 1755. Related: Incubated; incubating.
incubus (n.)
"imaginary being or demon, credited with causing nightmares, and, in male form, consorting with women in their sleep," c. 1200, from Late Latin incubus (Augustine), from Latin incubo "nightmare, one who lies down on (the sleeper)," from incubare "to lie upon" (see incubate). Plural is incubi. Compare succubus.
inculcate (v.)
"enforce or stamp upon the mind," especially by admonitions or forcible statement, 1540s, from Latin inculcatus, past participle of inculcare "force upon, insist; stamp in, impress, tread down," from in- "in" (from PIE root *en "in") + calcare "to tread, press in," from calx (1) "heel" (see calcaneus). Related: Inculcated; inculcating.
inculcation (n.)
"act of impressing upon the mind by repeated admonitions; forcible or persistent teaching," 1550s, from inculcate (v.), or else Late Latin inculcationem (nominative inculcatio), noun of action from past-participle stem of inculcare "to force upon; stamp in."
inculpable (adj.)
"not meriting blame, innocent," late 15c., from Late Latin inculpabilis "unblameable," from in- "not, opposite of" (see in- (1)) + culpabilis "guilt" (see culpable).
inculpate (v.)
"to accuse, bring charges against," 1794, from Medieval Latin inculpatus, past participle of inculpare "to reproach, blame, censure," from Latin in- "in" (from PIE root *en "in") + culpare "to blame," from culpa "fault." But inculpable (late 15c.) means "not culpable, free from blame," from Latin in- "not" (see in- (1)) + culpare.
inculpation (n.)
"incrimination," 1798, noun of action from inculpate (v.). Perhaps from or modeled on French inculpation (18c.).
incumbency (n.)
"state of being an incumbent," c. 1600, from incumbent + abstract noun suffix -cy.
incumbent (adj.)
"lying or resting on something," 1560s, originally "lying or resting on as a duty or obligation, imposed," from Medieval Latin incumbentem (nominative incumbens), present participle of incumbere (see incumbent (n.)). The literal, physical sense "lying or resting on something" is attested from 1620s but is rare in English.
incumbent (n.)
early 15c., "person holding a church position," from Medieval Latin incumbentem (nominative incumbens) "holder of a church position," noun use of present participle of incumbere "to obtain or possess," from Latin incumbere "recline on," figuratively "apply oneself to," from in- "on" (from PIE root *en "in") + -cumbere "lie down," related to cubare "to lie" (see cubicle). Extended to holders of any office from 1670s.
incumbrance (n.)
see encumbrance.
incunabula (n.)
1824, a Latin word meaning "swaddling clothes," also, figuratively, "childhood, beginnings, birthplace, place where a thing had its earliest development, the beginning of anything;" especially "early printed book using movable-type technology," From Gutenberg's beginning c. 1439 to the close of the year 1500. Latin incunabula "a cradle; a birthplace," figuratively "rudiments or beginnings," is from in "in" (from PIE root *en "in") + cunabula, diminutive of cunae "cradle," from PIE *koi-na-, suffixed form of root *kei- (1) "to lie," also forming words for "bed, couch."
Interest in collecting them began c. 1640 with the celebration of (as it was supposed) the 200th anniversary of printing. Perhaps this use of the word traces to the title of the first catalog of such books, Incunabula typographiae (Amsterdam, 1688). The word in this sense has come into general use throughout Europe. The number of books put on the market throughout Europe during that period has been estimated at 20 million. Prof. Alfred W. Pollard [Encyclopaedia Britannica, 1941] wrote that "up to the end of the 17th century," Caxton's original printings "could still be bought for a few shillings."
incunabulum (n.)
1861, singular of Latin incunabula "cradle, birthplace; rudiments or beginnings" (see incunabula); taken up (originally in German) as a word for any book printed late 15c., in the infancy of the printer's art.
incur (v.)
c. 1400, "bring (an undesirable consequence) upon oneself;" mid-15c. as "become liable for (payment or expenses)," from Anglo-French encurir, Old French encorir "to run, flee; commit, contract, incur" (Modern French encourir), from Latin incurrere "run into or against, rush at, make an attack;" figuratively, "to befall, happen, occur to," from in- "upon" (from PIE root *en "in") + currere "to run" (from PIE root *kers- "to run"). Related: Incurred; incurring.
incurable (adj.)
"beyond the power or skill of medicine," mid-14c., from Old French incurable "not curable" (13c.), from Late Latin incurabilis "not curable," from in- "not" (see in- (1)) + curabilis "curable" (see curable). As a noun, "incurable person," from 1650s. Related: Incurably.
incurious (adj.)
1560s, "negligent, heedless," from Latin incuriosus "careless, negligent, unconcerned," from in- "not, opposite of, without" (see in- (1)) + curiosus (see curious). Meaning "uninquisitive" is from 1610s. Objective sense of "unworthy of attention" is from 1747. Related: Incuriously. Incuriosity is attested from c. 1600.
incursion (n.)
"hostile attack," early 15c., from Old French incursion "invasion, attack, assault" (14c.) or directly from Latin incursionem (nominative incursio) "a running against, hostile attack," noun of action from past participle stem of incurrere "run into or against, rush at" (see incur).
in custodia legis (adv.)
legal Latin, "in the custody of the law," from ablative of custodia "a guarding, watching, keeping" (see custody) + legis, genitive of lex "law" (see legal (adj.)).
indeed (adv.)
c. 1600, a contraction into one word of the prepositional phrase in dede "in fact, in truth, in reality" (early 14c.), from Old English dæd "a doing, act, action, event" (see deed (n.)). As an interjection, 1590s; as an expression of surprise or disgust, 1834. Emphatic form yes (or no) indeedy attested from 1856, American English.
indearing (adj.)
see endearing.
indear (v.)
see endear.
indebted (adj.)
late 14c., endetted "owing money, liable for borrowed money," past participle of endetten "to indebt, oblige," from Old French endeter "to involve in debt, run into debt," from en- "in" (from PIE root *en "in") + dete "debt" (see debt). Figurative sense of "under obligation for favors or services" first attested 1560s. Spelling re-Latinized in English from 16c. The verb indebt is now rare or obsolete. Related: Indebtedness. Latin indebitus meant "not owed, not due."
indecent (adj.)
1560s, "unbecoming, in bad taste," from French indécent (14c.) or directly from Latin indecentem (nominative indecens) "unbecoming, unseemly," from in- "not, opposite of, without" (see in- (1)) + decens "becoming, seemly, fitting, proper," present participle of decere "to be fitting or suitable," from PIE *deke-, from root *dek- "to take, accept." Sense of "offending against propriety" is from 1610s. Indecent assault (1861) originally covered sexual assaults other than rape or intended rape, but by 1934 it was being used as a euphemism for "rape." Related: Indecently
indecency (n.)
1580s, "outrageous conduct," from Latin indecentia "unseemliness, impropriety," abstract noun from indecentem "unbecoming" (see indecent). Now especially of conduct which violates recognized standards of propriety (1690s).
indecipherable (adj.)
1802, from in- (1) "not" + decipherable (see decipher (v.)). Undecipherable is older. Related: Indecipherably; indecipherability.
indecision (n.)
1735, from in- (1) "not, opposite of, without" + decision. Perhaps from or modeled on French indécision (17c.), which Cotgrave's "French and English Dictionary" (1673) translates with An undecision.
indecisive (adj.)
1726, "inconclusive," from in- (1) "not, opposite of" + decisive. Meaning "vacillating, characterized by indecision" is from 1775. Related: Indecisively; indecisiveness.
indeclinable (adj.)
late 14c., originally in grammar, from French indéclinable or directly from Latin indeclinabilis "unchangeable," also in grammar, from indeclinatus "unchanged, constant," from in- "not, opposite of" (see in- (1)) + declinatus, from declinare "to lower; avoid, deviate; bend from, inflect" (see decline (v.)). Related: Indeclinably.
indecorous (adj.)
1680s, "in bad taste," from Latin indecorus "unbecoming, unseemly, unsightly; disgraceful," from in- "not, opposite of, without" (see in- (1)) + decorus "becoming, fitting, seemly, proper" (see decorous). Related: Indecorously; indecorousness (1670s).
indecorum (n.)
1570s, from Latin indecorum, noun use of neuter of adjective indecorus "unbecoming, unseemly, unsightly" (see indecorous).
indefatigable (adj.)
1580s (implied in indefatigably), from French indefatigable (15c.), from Latin indefatigabilis "that cannot be wearied," from in- "not" (see in- (1)) + defatigare "to tire out," from de- "utterly, down, away" (see de-) + fatigare "to weary" (see fatigue (n.)).
Blount's "Glossographia" (1656) has defatigable, which also was in use elsewhere in 17c., but the modern use of defatigable (1948) probably is a jocular back-formation from indefatigable.
indefatigability (n.)
1630s, from indefatigable + -ity. Indefatigableness is from 1650s; indefatigation from 1640s.
indefeasible (adj.)
"not to be set aside or overcome," 1530s (implied in indefeasibly), from in- (1) "not, opposite of" + defeasible (see defeasance).
indefensible (adj.)
1520s, "that cannot be maintained or justified by argument," from in- (1) "not, opposite of" + defensible. From 1560s as "that cannot be maintained by force." Related: Indefensibly.
indefinable (adj.)
"incapable of being exactly described," 1721, from in- (1) "not, opposite of" + definable (see define). Related: Indefinably.
indefinability (n.)
1814, from indefinable + -ity.
indefinitely (adv.)
early 15c., "without settled limitation, boundless;" see indefinite + -ly (2).
indefinite (adj.)
1520s, "not precise, vague," from Latin indefinitus "indefinite," from in- "not, opposite of, without" (see in- (1)) + definitus, past participle of definire (see define). In reference to number, "The term was introduced by Pascal. Descartes distinguished between the indefinite, which has no particular limit, and the infinite which is incomparably greater than anything having a limit. The distinction is considered as highly important by many metaphysicians." [Century Dictionary]
indelible (adj.)
1520s, from Latin indelebilis "indelible, imperishable," from in- "not, opposite of, without" (see in- (1)) + delebilis "able to be destroyed," from delere "destroy, blot out" (see delete). Vowel change from -e- to -i- in English is late 17c. Related: Indelibly.
indelicate (adj.)
1670s, "offensive to a refined sense of propriety, beyond the bounds of proper reserve," from in- (1) "not, opposite of" + delicate. Related: Indelicately.