Old English undon "to unfasten and open" (a window or door), "to unfasten by releasing from a fixed position; to cancel, discharge, abrogate, reverse what has been done, put back in a former condition; bring to ruin, destroy," from un- (2) "opposite of" + do (v.). Related: Undone; undoing.

undocumented (adj.)

1883, from un- (1) "not" + past participle of document (v.).

undomesticated (adj.)

1787, of women, "unsuited to home life," 1813, of animals, "not brought under control of humans," from un- (1) "not" + past participle of domesticate (v.). Undomestic "not caring for home life" is recorded from 1754.

undone (adj.)

"not accomplished," c. 1300, from un- (1) "not" + done. The same word meaning "destroyed" is recorded from mid-14c., past-participle adjective from undo.

undoubted (adj.)

mid-15c., from un- (1) "not" + past participle of doubt (v.). Related: Undoubtedly.

undoubtable (adj.)

early 15c., from un- (1) "not" + doubt (v.) + -able. Related: Undoubtably.

undreamed (adj.)

1610s, from un- (1) "not" + past participle of dream (v.).

undress (v.)

1590s, "to shed one's clothing," from un- (2) "opposite of" + dress (v.). Transitive sense of "to strip off (someone's) clothing" is recorded from 1610s. Related: Undressed; undressing.

undressed (adj.)

"naked (or nearly so)," 1610s, past-participle adjective from undress (v.).

undress (n.)

"state of partial or incomplete dress," 1680s, from undress (v.). Meaning "ordinary dress" is from 1748.

undue (adj.)

late 14c., "not owing or payable; unjustly demanded," also "not appropriate, unseasonable," also "excessive," from un- (1) "not" + past participle of due (v.). Formed on model of Old French indeu, Latin indebitus.

undulation (n.)

1640s, from Medieval Latin *undulatio, from Late Latin undulatus "wavy, undulated," from undula "wavelet," diminutive of Latin unda "a wave," from PIE *unda-, nasalized form of root *wed- (1) "water; wet."

undulant (adj.)

1830, from Latin undulantem (nominative undulans), from unda "a wave," from PIE *unda-, nasalized form of root *wed- (1) "water; wet."

undulate (v.)

"to move in waves," 1660s, back-formation from undulation. Related: undulated, undulating.

unduly (adv.)

late 14c., "without due moderation; improperly, unsuitably;" see undue + -ly (2). From early 15c. as "unjustly, wrongfully."

unearned (adj.)

c. 1200, from un- (1) "not" + past participle of earn (v.). Unearned income is recorded from 1889.

unearth (v.)

"to dig up," mid-15c., from un- (2) "opposite of" + earth (v.) "bury (a corpse) in the ground" (c. 1400, from earth (n.)). Related: Unearthed; unearthing.

unearthly (adj.)

1610s, "heavenly, sublime," from un- (1) "not" + earthly. Sense of "ghostly, weird" is attested by 1802. Related: Unearthliness.

uneasy (adj.)

late 13c., "not comforting, causing trouble," from un- (1) "not" + easy (adj.). Meaning "disturbed in mind" is attested from 1670s. Related: Uneasily; uneasiness.

uneducated (adj.)

1580s, from un- (1) "not" + past participle of educate (v.).

unelectable (adj.)

also un-electable, 1962, from un- (1) "not" + electable.

unemancipated (adj.)

1775, from un- (1) "not" + past participle of emancipate (v.).

unemotional (adj.)

1819, from un- (1) "not" + emotional (adj.). Related: Unemotionally.

unemployed (adj.)

1600, "at leisure, not occupied," from un- (1) "not" + past participle of employ (v.). Meaning "temporarily out of work" is from 1660s. There seems not to have been a verb *unemploy, but disemploy was used (1610s). The noun meaning "unemployed persons collectively" is from 1782.

unemployment (n.)

1887, from un- (1) "not" + employment.

unencumbered (adj.)

1722, from un- (1) "not" + past participle of encumber (v.).

unending (adj.)

1660s, from un- (1) "not" + present participle of end (v.).

unendurable (adj.)

1620s, from un- (1) "not" + endurable. Related: Unendurably.

un-English (adj.)

"lacking in qualities regarded as typically English," 1630s, from un- (1) "not" + English (adj.).

unenlightened (adj.)

1660s, "not lit up," from un- (1) "not" + past participle of enlighten (v.). Meaning "not mentally illuminated" is attested from 1650s.

unenthusiastic (adj.)

1805, from un- (1) "not" + enthusiastic (adj.). Related: Unenthusiastically.

unenviable (adj.)

1640s, from un- (1) "not" + enviable (adj.). Related: Unenviably.

unequal (adj.)

1530s, "unjust, unfair," from un- (1) "not" + equal (adj.). Meaning "not the same in amount, size, quality, etc." is recorded from 1560s (inequal in this sense is from late 14c.). Sense of "inadequate, insufficient" (to some task) is attested from 1690s. Related: Unequally.

unequivocal (adj.)

1784, from un- (1) "not" + equivocal. Related: Unequivocally.

unerring (adj.)

1640s (implied in unerringly), from un- (1) "not" + verbal noun from err. Related: Unerringly.

UNESCO

acronym from United Nations Educational, Scientific and Cultural Organization, which was created in 1945.

unethical (adj.)

1871, from un- (1) "not" + ethical. Related: Unethically.

uneventful (adj.)

1800, from un- (1) "not" + eventful. Related: Uneventfully.

uneven (adj.)

Old English unefen "unequal, unlike, anomalous, irregular," from un- (1) "not" + even (adj.). Similar formation in Old Frisian oniovn, Middle Dutch oneven, Old High German uneban, German uneben, Old Norse ujafn. Meaning "broken, rugged" (in reference to terrain, etc.) is recorded from late 13c. Related: Unevenly; unevenness.

unevitable (adj.)

from un- (1) "not" + evitable. The usual word is inevitable. Related: Unevitably.

unexamined (adj.)

late 15c., from un- (1) "not" + past participle of examine (v.).

unexceptional (adj.)

from un- (1) "not" + exceptional (adj.).

unexceptionable (adj.)

1660s, from un- (1) "not" + exceptionable.

unexcusable (adj.)

late 14c., from un- (1) "not" + excusable. The usual word is inexcusable. Related: Unexcusably.

unexpected (adj.)

1580s, from un- (1) "not" + past participle of expect (v.). Related: Unexpectedly.

unexperienced (adj.)

1560s, from un- (1) "not" + past participle of experience (v.).

unexplained (adj.)

1721, from un- (1) "not" + past participle of explain (v.).

unexplainable (adj.)

1711, from un- (1) "not" + explain + -able. Related: Unexplainably.

unexplored (adj.)

1690s, from un- (1) "not" + past participle of explore (v.).

unexpurgated (adj.)

1882, from un- (1) "not" + past participle of expurgate (v.).

unfading (adj.)

from un- (1) "not" + past participle of fade (v.).

unfailing (adj.)

late 14c., "never coming to an end, unceasing, everlasting, inexhaustible," from un- (1) "not" + present participle of fail (v.). Related: Unfailingly.

unfairness (n.)

Old English unfægernes "ugliness, disfigurement;" see unfair + -ness.

unfair (adj.)

Old English unfægr "unlovely, not beautiful, deformed, hideous, unlovable," from un- (1) "not" + fair (adj.). Similar formation in Old Norse ufagr, Gothic unfagrs. The meaning "wicked, evil, bad" is recorded from c. 1300. The sense of "not equitable, unjust" is first attested 1713. Related: Unfairly.

unfaithful (adj.)

mid-14c., "acting falsely," from un- (1) "not" + faithful. In Middle English it had also a sense of "infidel, unbelieving, irreligious" (late 14c.). The meaning "not faithful in marriage" is attested from 1828. Related: Unfaithfully; unfaithfulness.

unfaltering (adj.)

1660s, from un- (1) "not" + present participle of falter (v.). Related: Unfalteringly.

unfamous (adj.)

late 14c., "not well known, obscure," from un- (1) "not" + famous (adj.). Also from late 14c. as "notably bad," a sense now in infamous.

unfamiliar (adj.)

1590s, from un- (1) "not" + familiar (adj.). Related: Unfamiliarly; unfamiliarity.

unfashionable (adj.)

1560s, "incapable of being shaped," from un- (1) "not" + fashionable. Meaning "not in accordance with prevailing fashion" is attested from 1640s. Related: Unfashionably.

unfasten (v.)

early 13c., from un- (2) "opposite of" + fasten. Old English had unfæstnian "to unfasten." Related: Unfastened; unfastening.

unfathomed (adj.)

1620s, from un- (1) "not" + past participle of fathom (v.).

unfathomable (adj.)

1610s, originally in the figurative sense, of feelings, conditions, etc., "too deep to be comprehended," from un- (1) "not" + fathomable. Literal sense of "too deep to be measured" is attested from 1670s. Related: Unfathomably.

unfavorable (adj.)

also unfavourable, mid-15c. (implied in unfavorably), from un- (1) "not" + favorable (adj.).

unfazed (adj.)

1933, American English, from un- (1) "not" + past participle of faze (v.).

unfeasible (adj.)

1520s, from un- (1) "not" + feasible.

unfeeling (adj.)

late Old English had unfelende, "having no sensation." Middle English had a verb unfeel "be insensible, fail to feel" (early 14c.) as well as unfeelingness "insensibility, loss of sensation," and unfeelingly "without understanding or direct knowledge" (late 14c.), and a verbal noun unfeeling "loss of sensation, lack of feeling." However the word in its main modern meaning "devoid of kindly or tender feelings" is from 1590s, from un- (1) "not" + past participle of feel (v.). Related: Unfeelingly.

unfeigned (adj.)

late 14c., "sincere, genuine, true, real," from un- (1) "not" + past participle of feign (v.).

unfelt (adj.)

1580s, from un- (1) "not" + past participle of feel (v.).

unfetter (v.)

mid-14c., from un- (2) "opposite of" + fetter (v.). The figurative sense is recorded from late 14c. Related: Unfettered; unfettering.

unfinished (adj.)

1550s, from un- (1) "not" + past participle of finish (v.).

unfit (v.)

"to render unfit," 1610s, from unfit (adj.), or else from un- (2) "reverse of" + fit (v.). Related: Unfitted; unfitting.

unfit (adj.)

1540s, "not suitable" (in reference to things), from un- (1) "not" + fit (adj.). Related: Unfitness. In reference to persons or human qualities, attested from 1550s.

unflagging (adj.)

1715, from un- (1) "not" + present participle of flag (v.). Related: Unflaggingly.

unflappable (adj.)

1958, from un- (1) "not" + flap (v.) + -able. Originally used in reference to Harold Macmillan, British P.M. 1957-63.

unflattering (adj.)

1580s, from un- (1) "not" + gerundive of flatter. Related: Unflatteringly.

unfledged (adj.)

c. 1600, of persons, "immature, not experienced," from un- (1) "not" + past participle of fledge (v.). Literal sense of "not yet covered in feathers" is recorded from 1610s.

unflinching (adj.)

1728, from un- (1) "not" + present-participle adjective of flinch (v.). Related: Unflinchingly.

unfold (v.)

Old English unfealdan, "to open or unwrap the folds of," also figuratively, "to disclose, reveal, explain," from un- (2) "opposite of" + fold (v.). Similar formation in Middle Dutch ontvouden, German entfalten. Intransitive sense is attested from late 14c. Related: Unfolded; unfolding.