Etymology dictionary
firefighter (n.) — flag (v.1)
firefighter (n.)
also fire-fighter, 1895, from fire (n.) + fighter.
fire-fight (n.)
also firefight, 1850, from fire (n.) in the military sense + fight (n.). A fight with guns and firearms (as opposed to hand-to-hand, etc.).
firefly (n.)
also fire-fly, "An insect which has the faculty of becoming luminous" [Century Dictionary], 1650s, from fire (n.) + fly (n.). Ancient Greek had kysolampis "firefly, beetle with a tail that lights up at night," from kysos, kysthos "buttocks" + lampein "to shine."
firelight (n.)
also fire-light, "light emitted by an open fire," Old English fyrleoht; see fire (n.) + light (n.).
firelock (n.)
type of gun lock that uses sparks to ignite the priming, 1540s, from fire (n.) + lock (n.1). Originally of the wheel-lock; transferred 17c. to the flintlock.
fireman (n.)
also fire-man, late 14c., "tender of a fire," from fire (n.) + man (n.). From 1650s as "furnace-tender" of a early steam engine. As "person hired to put out (rather than tend) fires" it is attested from 1714. For "stoker," Old English had fyrbeta.
fireplace (n.)
also fire-place, c. 1700, from fire (n.) + place (n.).
fireplug (n.)
also fire-plug, 1713, from fire (n.) + plug (n.).
firepower (n.)
also fire-power "effectiveness of military fire," 1891, from fire (n.) + power (n.).
fireproof (adj.)
also fire-proof, 1630s, from fire (n.) + proof. As a verb, from 1867. Related: Fireproofed; fireproofing.
fireside (n.)
also fire-side, 1560s, from fire (n.) + side (n.). Symbolic of home life by 1848. As an adjective from 1740s; especially suggesting the intimately domestic.
firestorm (n.)
also fire-storm, 1580s, in poetry, from fire (n.) + storm (n.). From 1945 in reality, in reference to nuclear war.
firetrap (n.)
also fire-trap, "place at great risk of destruction by fire and with insufficient means of escape," 1882, from fire (n.) + trap (n.).
firewall (n.)
also fire-wall, 1851 as a physical wall meant to prevent the spread of fire in a structure, from fire (n.) + wall (n.). Computer sense (originally figurative) is by 1990.
fire-walker (n.)
one who walks barefoot over hot coals without injury, as an entertainment, etc., 1895, from fire (n.) + agent noun from walk (v.). Related: Fire-walking.
firewater (n.)
also fire-water, "alcoholic liquor," 1826, American English, supposedly from speech of American Indians, from fire (n.) + water (n.1).
firewood (n.)
also fire-wood, late 14c., from fire (n.) + wood (n.).
fireworks (n.)
also fire-works, "pyrotechnic contrivances," 1570s, from fire (n.) + works. Figurative use from 1660s.
firkin (n.)
"small cask," late 14c., apparently from Middle Dutch *vierdekijn, diminutive of vierde, literally "fourth, fourth part" (from vier "four," from PIE root *kwetwer- "four"); so called because it usually is the fourth part of a barrel.
firm (v.)
c. 1300, fermen "make firm, establish," from Old French fermer "consolidate; fasten, secure; build, set up; fortify" (12c.) or directly from Latin firmare "make firm; affirm; strengthen, fortify, sustain; establish, prove, declare," from firmus "strong, steadfast, stable" (see firm (adj.)). Intransitive use, "become firm" is from 1879; with up (adv.) from 1956. Related: Firmed; firming.
firm (adj.)
late 14c., ferm, "strong, steady" (of things), "permanent, enduring" (of agreements), "steadfast, steady" (of persons), "sound, well-founded" (of arguments), from Old French ferm "strong, vigorous; healthy, sound; steadfast, loyal, faithful" (12c.), from Latin firmus "strong, steadfast, enduring, stable," figuratively "constant, steadfast, trusty, faithful," from suffixed form of PIE root *dher- "to hold firmly, support." The spelling return to -i- in late 1500s was modeled on Latin. Related: Firmly; firmness.
firm (n.)
"business house," 1744, according to Barnhart from German Firma "a business, name of a business," originally "signature," from Italian firma "signature," from firmare "to sign," from Latin firmare "make firm, affirm," in Late Latin, "confirm (by signature)," from firmus "strong; stable," figuratively "constant, trusty" (see firm (adj.)).
firmament (n.)
mid-13c., "expanse of space above the earth where the heavenly bodies move," hence "the arch or vault of the heavens, the visible sky" (c. 1300), from Old French firmament or directly from Latin firmamentum "firmament," literally "a support, a strengthening," from firmus "strong, steadfast, enduring" (from suffixed form of PIE root *dher- "to hold firmly, support" ).
Used in Late Latin in the Vulgate to translate Greek stereoma "firm or solid structure," which translated Hebrew raqia, a word used of both the vault of the sky and the floor of the earth in the Old Testament, probably literally "expanse," from raqa "to spread out," but in Syriac meaning "to make firm or solid," hence the erroneous translation.
In Ptolemaic astronomy, "the sphere of the fixed stars" (c. 1300). Related: Firmamental.
firmware (n.)
"permanent software programmed into a read-only memory and providing the low-level control for the device's hardware," 1968, from firm (adj.) + ending from software.
firn (n.)
"consolidated snow, the raw material of glaciers," 1839, literally "last year's snow, névé," from German Firn, from Swiss dialectal firn "of last year," from Middle High German virne "old," from Old High German firni, related to Old English fyrn "old," Gothic fairns "of last year," from Proto-Germanic *fur- "before" (see fore (adv.)).
The only living English relic of a useful word meaning "of last year" that was widespread in Indo-European languages (cognates: Lithuanian pernai "last year" (adv.), Greek perysi "a year ago, last year," Sanskrit parut "of last year;" also German Firnewein "wine of last year"). Old English had fyrngemynd "ancient history," more literally, "memory of long ago;" fyrnmann "man of old times;" fyrnnes "antiquity;" fyrnsægen "old saying." Middle English retained fern "long ago, formerly, of old," fern-days "days of old, former year, a year past."
first (adj., adv.)
Old English fyrst "foremost, going before all others; chief, principal," also (though rarely) as an adverb, "at first, originally," superlative of fore; from Proto-Germanic *furista- "foremost" (source also of Old Saxon fuirst "first," Old High German furist, Old Norse fyrstr, Danish første, Old Frisian ferist, Middle Dutch vorste "prince," Dutch vorst "first," German Fürst "prince"), from PIE *pre-isto-, superlative of *pre-, from root *per- (1) "forward," hence "in front of, before, first, chief."
The usual Old English superlative word was not fyrst, but forma, which shows more clearly the connection to fore. Forma became Middle English firme "first, earliest," but this has not survived.
First aid is that given at the scene, pending the arrival of a doctor. First lady as an informal title for the wife of a U.S. president was in use by 1908, short for First lady of the land (by 1863 with reference to the president's wife); the earlier title was simply Lady (1841). First name is attested from mid-13c. First base "a start" in any sense (1938) is a figurative use from baseball.
First fruits is from late 14c. as "earliest productions of the soil;" 1590s as "first results" of any activity or endeavor. First love is from 1741 as "one's first experience of romantic love;" 1971 as "one's favorite occupation or pastime." First floor is from 1660s as "story built on or just above the ground" (now U.S.); 1865 as "story built next above the ground."
first (n.)
1560s, "that which is first," from first (adj.). Meaning "first day of the month" is by 1590s. In music, "instrument or voice that takes the highest or chief part of its class," 1774. From 1909 as the name of the lowest gear in an engine. In British schools colloquial use, "highest rank in an examination," 1850.
first-born (adj., n.)
"first in order of birth," as a noun, "first-born child," mid-14c., from first (adj.) + born.
first-class (adj.)
"of the highest class" with reference to some standard of excellence, 1837, from first (adj.) + class (n.). Specifically in reference to conveyances for travel, 1846. In reference to U.S. Mail, 1875.
first-hand (adj.)
also firsthand, "direct from the source or origin," 1690s, from the image of the "first hand" as the producer or maker of something.
firstly (adv.)
"in the first place, before anything else," 1530s, but never a common word (simple first usually serving its place), from first + -ly (2).
first-rate (adj.)
"of the highest excellence," 1660s, from first (adj.) + rate (n.) in a specific sense "class of warships in the British Navy." As a mere emphatic statement expressing excellence, by 1812. Colloquially, as a quasi-adverb, 1844.
first-timer (n.)
"rookie, one doing something for the first time," 1888, from first time; see first (adj.) + time (n.).
firth (n.)
"arm of the sea, estuary of a river," early 15c., Scottish, from Old Norse fjörðr (see fjord).
fiscal (adj.)
1560s, "pertaining to public revenue," from French fiscal, from Late Latin fiscalis "of or belonging to the state treasury," from Latin fiscus "state treasury," originally "money bag, purse, basket made of twigs (in which money was kept)," which is of unknown origin. The etymological notion is of the public purse. The general sense of "financial" (1865, American English) was abstracted from phrases fiscal calendar, fiscal year, etc. Related: Fiscally.
fishing (n.)
"the art or practice of trying to catch fish," c. 1300, fysschynge, verbal noun from fish (v.). Figurative use from 1540s. The Old English noun was fiscað.
Fishing-boat is from 1732. Fishing rod (1550s) is older than fishing pole (1791). To "go fishing" is as old as Old English on fiscoð gan.
fish (n.)
"a vertebrate which has gills and fins adapting it for living in the water," Old English fisc "fish," from Proto-Germanic *fiskaz (source also of Old Saxon, Old Frisian, Old High German fisc, Old Norse fiskr, Middle Dutch visc, Dutch vis, German Fisch, Gothic fisks), perhaps from PIE root *pisk- "a fish." But Boutkan on phonetic grounds thinks it might be a northwestern Europe substratum word.
Popularly, since Old English, "any animal that lives entirely in the water," hence shellfish, starfish (an early 15c. manuscript has fishes bestiales for "water animals other than fishes"). The plural is fishes, but in a collective sense, or in reference to fish meat as food, the singular fish generally serves for a plural. In reference to the constellation Pisces from late 14c.
Fish (n.) for "person" is from 1750 with a faintly dismissive sense; earlier it was used in reference to a person considered desirable to "catch" (1722). Figurative sense of fish out of water "person in an unfamiliar and awkward situation" attested by 1610s (a fisshe out of the see in the same sense is from mid-15c.). To drink like a fish is from 1744. To have other fish to fry "other objects which invite or require attention" is from 1650s. Fish-eye as a type of lens is from 1961. Fish-and-chips is from 1876; fish-fingers from 1962.
fish (v.)
Old English fiscian "to fish, to catch or try to catch fish" (cognates: Old Norse fiska, Old High German fiscon, German fischen, Gothic fiskon), from the root of fish (n.). Related: Fished; fishing.
fishbowl (n.)
also fish-bowl, "a glass globe in which fish are kept," 1850, from fish (n.) + bowl (n.). The form goldfish-bowl is attested from 1841. Figuratively, as a place where one is under constant observation, by 1957. Fish-globe is by 1858.
fisher (n.)
Old English fiscere "fisherman; kingfisher," agent noun from fish (v.). It began to be used of certain animals, hence perhaps the rise of the formation fisherman (1520s). Similar formation in Old Saxon fiskari, Old Frisian fisker, Dutch visscher, German Fischer, Old Norse fiskari.
fishery (n.)
"business of fishing," 1670s; "place where fish are caught," 1690s; see fish (v.) + -ery. Related: Fisheries.
fisherman (n.)
1520s, from fisher + man (n.).
fish-food (n.)
1863, "food for (pet or hobby) fish;" 1860, "fish as food for humans;" from fish (n.) + food.
fish-hook
late 14c., from fish (n.) + hook (n.).
fishy (adj.)
late 15c., "fish-like, slimy," from fish (n.) + -y (2). In reference to taste, from 1540s. Sense of "shady, questionable" is first recorded 1840, perhaps from the notion of "slipperiness," or of giving off a bad odor.
fishmonger (n.)
also fish-monger, mid-15c., from fish (n.) + monger (n.).
fishnet (n.)
"net used to catch fish," Old English fiscnett; see fish (n.) + net (n.). From 1881 in reference to a type of stitch that resembles fishnet. By 1912 in reference to women's hosiery.
fishpond (n.)
also fish-pond, mid-15c., from fish (n.) + pond (n.).
fish-story (n.)
"incredible or extravagant narration," by 1819, U.S. colloquial, from the tendency to exaggerate the size of the catch (or the one that got away). See fish (n. ) + story (n.1).
Snake-story in the same sense (in telling how long it was) is attested by 1823, American English.
fish-tail (n.)
1840, "the tail of a fish," from fish (n.) + tail (n.). As a verb, also fishtail, 1927, originally of aircraft, later automobiles. Related: Fishtailed; fishtailing.
fish-tank (n.)
1921 as an ornamental object, from fish (n.) + tank (n.1).
fishwife (n.)
1520s, from fish (n.) + wife (n.) in the "woman" sense. Also fish-fag.
fisk (v.)
2002, an internet argument tactic involving a reprinting of a text, interlarded with rebuttals and refutations. Named for English journalist Robert Fisk (b.1946), Middle East correspondent for the "Independent," whose writing often criticizes America and Israel and is somewhat noted for looseness with details. Critics responded in this style. Related: Fisked; fisking.
fissile (adj.)
1660s, from Latin fissilis "that which may be cleft or split," from fissus, past participle of findere "cleave, split, separate, divide" (from PIE root *bheid- "to split").
fission (n.)
1819, "division of a cell or organism," from Latin fissionem (nominative fissio) "a breaking up, cleaving," from past participle stem of findere "to split" (from PIE root *bheid- "to split"). Cognate with Old English bitan "to bite." Nuclear physics sense is 1939. As a verb, from 1929.
fissure (n.)
c. 1400, from Old French fissure (13c.) and directly from Latin fissura "a cleft," from root of findere "to split, cleave, separate, divide," from PIE *bhind-, nasalized form of root *bheid- "to split."
fistful (n.)
"as much as a fist will hold," 1610s, from fist (n.) + -ful.
fist (n.)
Old English fyst "fist, clenched hand," from West Germanic *fusti- (source also of Old Saxon fust, Old High German fust, Old Frisian fest, Middle Dutch vuust, Dutch vuist, German Faust), from Proto-Germanic *funhstiz, probably ultimately from a PIE "hand" word that is ultimately cognate with the root *penkwe- "five" (compare Old Church Slavonic pesti, Russian piasti "fist"), in reference to the five fingers.
Meaning "a blow with the fist" is from 1767. Fist-fight "duel with the fists" is from c. 1600. As a verb, Old English had fystlian "to strike with the fist."
fistiana (n.)
"anecdotes of pugilists; boxing lore," 1839, from fist (n.) + -iana.
fistic (adj.)
"relating to or done with the fists," 1806, from fist (n.) + -ic. Long considered improper English ("Not in dignified use" - OED).
fisticuffs (n.)
c. 1600, fisty cuffes, from fist (n.) + cuff (n.) "a blow" (see cuff (v.2)), with the form perhaps in imitation of handiwork. Related: Fisticuff.
fistula (n.)
"long, narrow ulcer," late 14c., from Latin fistula "a pipe; ulcer," which is of uncertain origin. Related: Fistular; fistulous (Latin fistulosus "full of holes; tubular").
fitting (adj.)
"proper, befitting, right," early 15c., present-participle adjective from fit (v.). Related: Fittingly.
fit (adj.)
"suited to the circumstances, proper," mid-15c., of unknown origin, perhaps from Middle English noun fit "an adversary of equal power" (mid-13c.), which is perhaps connected to fit (n.1). In athletics, "in condition, properly trained for action," from 1869. Related: Fitter; fittest. Survival of the fittest (1867) coined by H. Spencer.
fitting (n.)
c. 1600, verbal noun from fit (v.). Meaning "action of fitting on a garment" is from 1900.
fit (v.)
c. 1400, "to marshal or deploy (troops);" early 15c. as "be fitting or proper, be suitable," from fit (adj.) and perhaps in part from Scandinavian (compare Old Norse fitja "knit"). From 1580s as "be the right shape." Transitive sense of "provide with what is suitable" is from 1590s; that of "make fit or suitable, bring into corresponding form or condition" is from c. 1600. Related: Fitted; fitting. Fitted sheets is attested from 1948.
fit (n.1)
1680s, "process of fitting," from fit (v.). From 1823 as "the fitting of one thing to another;" 1831 as "the way something fits."
fit (n.2)
"paroxysm, sudden attack" (as of anger), 1540s, probably via Middle English fit (n.) "painful, exciting experience" (early 14c.), from Old English fitt "conflict, struggle," which is of uncertain origin, with no clear cognates outside English. Perhaps it is ultimately cognate with fit (adj.) on the notion of "to meet." The meaning "sudden impulse toward activity or effort" is from 1580s.
Phrase by fits and starts is attested by 1610s (see start (n.)); by fits is from 1580s and Middle English had stertmele "irregularly, by fits and starts" (early 15c.).
fitful (adj.)
used once by Shakespeare ("Life's fitful fever," "Macbeth," 1605) in sense of "characterized by fits," from fit (n.2) + -ful. then Revived in Romantic poetry late 18c. with a sense of "shifting, changing." Related: Fitfully (1792); fitfulness.
fitness (n.)
1570s, "state or quality of being suitable," from fit (adj.) + -ness. Meaning "state of being physically fit" is from 1935.
fit (n.3)
part of a poem, Old English fitt, of unknown origin; perhaps related to fit (n.2).
fitter (n.)
1650s, agent noun from fit (v.).
fitz (n.)
Anglo-French fitz, from Old French fils, from Latin filius "son of" (see filial); used regularly in official rolls and hence the first element of many modern surnames; in later times used of illegitimate issue of royalty.
five (num.)
"1 more than four; the number which is one more than four; a symbol representing this number;" Old English fif "five," from Proto-Germanic *fimfe (source also of Old Frisian fif, Old Saxon fif, Dutch vijf, Old Norse fimm, Old High German funf, Gothic fimf), from PIE root *penkwe- "five." The lost *-m- is a regular development (compare tooth).
Five-and-ten (Cent Store) is from 1880, American English, with reference to prices of goods for sale. Five-star (adj.) is from 1913 of hotels, 1945 of generals. Slang five-finger discount "theft" is from 1966. The original five-year plan was 1928 in the U.S.S.R. Five o'clock shadow attested by 1937.
fivefold (adv.)
1570s, from earlier use as an adjective, from Old English fiffeald (adj.); see five + -fold.
fiver (n.)
1843, "five-pound note," from five + -er.
fix (n.)
"position from which it is difficult to move," 1809, American English, from fix (v.). Meaning "dose of narcotic" is from 1934, shortened from fix-up (1867, originally in reference to liquor). Meaning "reliable indication of the position of a ship, plane, etc." (by reference to fixed positions) is from 1902.
fixative (adj.)
1640s, from fix (v.) + -ative, suffix meaning "of or related to; tending to." As a noun, from 1870, "that which fixes."
fix (v.)
late 14c., "set (one's eyes or mind) on something" (a figurative use), probably from Old French verb *fixer, from fixe "fixed," from Latin fixus "fixed, fast, immovable; established, settled," past-participle adjective from figere "to fix, fasten, drive, thrust in; pierce through, transfix," also figurative, from PIE root *dheigw- "to pierce, stick in;" hence "to fix, fasten."
Sense of "fasten, attach" is c. 1400; that of "to make (colors, etc.) fast or permanent" is from 1660s. The meaning "settle, assign" evolved into "adjust, arrange" (1660s), then "to repair" (1737), but this sometimes was objected to (see below). Sense of "tamper with" (a fight, a jury, etc.) is from 1790. As euphemism for "castrate a pet" it dates from 1930. Related: Fixed; fixing.
fixed (adj.)
late 14c., of stars, "unchangeable in position," past-participle adjective from fix (v.). Related: fixedly (1590s). Fixed-income (n.) is from 1767.
fixings (n.)
"apparatus," 1820, American English, from fixing "act of putting in order" (c. 1600), verbal noun from fix (v.). American English sense of "food, garnishing" is attested from 1839.
fixable (adj.)
late 15c., from fix (v.) + -able.
fixate (v.)
1885, "to fix, make stable," from fix (v.) + -ate. Meaning "to gaze upon" is from 1889. Psychological sense is from 1926, originally in Freudian theory, in this case perhaps a back-formation from fixation. Meaning "become fixed" is from 1888. Related: Fixated; fixating.
fixation (n.)
late 14c., fixacion, an alchemical word, "action of reducing a volatile substance to a permanent bodily form," from Medieval Latin fixationem (nominative fixatio), noun of action from past-participle stem of Latin fixare, frequentative of figere "to fasten, fix" (from PIE root *dheigw- "to stick, fix"). Meaning "condition of being fixed" is from 1630s. Used in the Freudian sense since 1910.
fixer (n.)
1849, of chemicals, etc.; 1885 as a person who "makes things right;" agent noun from fix (v.). Fixer-upper is from 1967 as "that which repairs other things" (in an advertisement for a glue); by 1976 as a real-estate euphemism for "property that needs a lot of work."
fixity (n.)
1660s in physics; general use from 1791; see fix (v.) + -ity.
fixture (n.)
1590s, "act of fixing," perhaps from fix (v.) on model of mixture, or from an assumed Latin *fixitatem. Meaning "anything fixed or securely fastened" is from 1812, an alteration of fixure (c. 1600).
fizgig (n.)
"light, frivolous woman," 1520s, first element of uncertain origin, second element is Middle English gig "frivolous person" (see gig (n.1)).
fizz (v.)
"make a hissing sound," 1660s, of imitative origin. Related: Fizzed; fizzing. The noun is recorded from 1812; meaning "effervescent drink" is from 1864, from the sound it makes.
fizzy (adj.)
fizzle (v.)
1530s, "to break wind without noise," probably altered from obsolete fist, from Middle English fisten "break wind" (see feisty) + frequentative suffix -le. Related: Fizzled; fizzling.
Meaning "make a noise as of a liquid or gas forced out a narrow aperture" is from 1859, "usually with special reference to the weakness and sudden diminution or cessation of such sound" [Century Dictionary], hence the figurative sense "prove a failure, stop abruptly after a more-or-less brilliant start." But this sense is earlier and dates to at least 1847 in American English college slang, along with the noun sense of "failure, fiasco" (1846), also originally U.S. college slang, "a failure in answering an examination by a professor." Barnhart says it is "not considered as derived from the verb." Halliwell ("Archaic and Provincial Words," 1846) has fizzle (v.) as "To do anything without noise," which might connect the college slang with the older word via some notion of mumbled and stifled performance:
fjord (n.)
1670s, from Norwegian fiord, from Old Norse fjörðr "an inlet, estuary," from North Germanic *ferthuz "place for crossing over, ford," from PIE *pertu-, from root *per- (2) "to lead, pass over." The etymological sense probably is "a going, a passage."
flab (n.)
"fat, flabbiness," 1951, back-formation from flabby.
flabbergasted (adj.)
see flabbergast.
flabbergast (v.)
1772, flabbergasted, mentioned (with bored) in a magazine article that year as a new vogue word, of uncertain origin. Perhaps from some dialect (in 1823 flabbergast was noted as a Sussex word), perhaps ultimately an arbitrary formation alluding to flabby or flapper and aghast. "Like many other popular words expressing intensity of action, ... not separable into definite elements or traceable to a definite origin" [Century Dictionary]. Related: Flabbergasted; flabbergasting; flabbergastation.
flabby (adj.)
1690s, regarded as a softened variant of flappy, which is recorded in the sense of "softly fleshy" from 1590s; see flap (n.). Related: Flabbily; flabbiness.
flaccid (adj.)
1610s, from French flaccide or directly from Latin flaccidus "flabby, pendulous, weak, drooping," from flaccus "flabby, flap-eared," which is of uncertain origin (OED suggests it's imitative). Related: Flaccidly; flacidness; flaccidity; flaccescency.
flack (n.)
"publicity or press agent," in Variety headlines by September 1933; sometimes said to be from name of Gene Flack, a movie agent, but influenced later by flak. There was a Gene Flack who was an advertising executive in the U.S. during the 1940s, but he seems to have sold principally biscuits, not movies, and seems not to have been in Variety in the '30s.
flag (v.2)
1875, "place a flag on or over," from flag (n.1). Meaning "designate as someone who will not be served more liquor," by 1980s, probably from use of flags to signal trains, etc., to halt, which led to a verb meaning "inform by means of signal flags" (1856, American English). Meaning "to mark so as to be easily found" is from 1934 (originally by means of paper tabs on files). Related: Flagged; flagger; flagging.
flag (n.1)
"cloth ensign," late 15c., now in all modern Germanic languages (German Flagge, Dutch vlag, Danish flag, Swedish flagg, etc.) but apparently first recorded in English, of unknown origin, but likely connected to flag (v.1) or else an independent imitative formation "expressing the notion of something flapping in the wind" [OED]. A guess considered less likely is that it is from flag (n.2) on the notion of being square and flat.
Meaning "name and editorial information on a newspaper" is by 1956. U.S. Flag Day (1894) is in reference to the adopting of the Stars and Stripes by the Continental Congress on June 14, 1777.
flag (v.1)
1540s, "flap about loosely," probably a later variant of Middle English flakken, flacken "to flap, flutter" (late 14c.), which probably is from Old Norse flaka "to flicker, flutter, hang loose," itself perhaps imitative of something flapping lazily in the wind. The sense of "go limp, droop, become languid" is attested by 1610s. Related: Flagged; flagging.