fireworks (n.) Look up fireworks at Dictionary.com
1570s, from fire (n.) + works (see work (n.)).
firkin (n.) Look up firkin at Dictionary.com
"small cask, fourth part of a barrel," late 14c., apparently from Middle Dutch *vierdekijn, diminutive of vierde, literally "fourth, fourth part" (see fourth).
firm (adj.) Look up firm at Dictionary.com
late 14c., from Old French ferm (12c.) "firm, strong, vigorous, steadfast; loyal, faithful," from Latin firmus "firm, strong, steadfast, enduring, stable," from PIE root *dher- (1) "to hold, support" (cognates: Sanskrit dharmah "custom, law," Greek thronos "seat," Lithuanian dirzmas "strong," Welsh dir "hard," Breton dir "steel"). The return in late 1500s to -i- from Middle English ferme was modeled on Latin. Related: Firmly; firmness.
firm (n.) Look up firm at Dictionary.com
"business house," 1744, 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 "firm, stable" (see firm (adj.)).
firm (v.) Look up firm at Dictionary.com
c.1300, fermen "make firm, establish," from Old French fermer (12c.) or directly from Latin firmare, from firmus (see firm (adj.)). Related: Firmed; firming.
firmament (n.) Look up firmament at Dictionary.com
mid-13c., from Latin firmamentum "firmament," literally "a support or strengthening," from firmus "firm" (see firm (adj.)), used in 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.
firmware (n.) Look up firmware at Dictionary.com
1968, from firm (adj.) + ending from software.
firn (n.) Look up firn at Dictionary.com
"consolidated snow, the raw material of glaciers," 1853, 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-/*for- (see first). The only English relic of a useful word meaning "of last year" that was widespread in Indo-European languages. It has cognates in Lithuanian pernai "last year," Greek perysi "a year ago, last year," Sanskrit parut "of last year."
first (adj., adv.) Look up first at Dictionary.com
Old English fyrst "foremost," superlative of fore; from Proto-Germanic *furisto- (cognates: 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"), superlative of *fur-/*for-, from PIE root *per- (1) "forward, through" (see per).

First-class (adj.) is from 1837; first-rate (1660s) is from classes of warships in the British navy. 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). First name is attested from mid-13c.; first-born is from mid-14c. First base "a start" (1938) is a figurative use from the game of baseball.
firsthand (adj.) Look up firsthand at Dictionary.com
also first-hand, first hand, 1690s, from the image of the "first hand" as the source or origin of something.
firstly (adv.) Look up firstly at Dictionary.com
1530s, but never a common word (simple first usually serving its place), from first + -ly (2).
firth (n.) Look up firth at Dictionary.com
"arm of the sea, estuary of a river," early 15c., Scottish, from Old Norse fjörðr (see fjord).
fiscal (adj.) Look up fiscal at Dictionary.com
1560s, "pertaining to public revenue," from Middle French fiscal, from Late Latin fiscalis "of or belonging to the state treasury," from Latin fiscus "treasury," originally "purse, basket made of twigs (in which money was kept)," of unknown origin. The general sense of "financial" (1865, American English) was abstracted from phrases like fiscal calendar, fiscal year. Related: Fiscally.
fish (n.) Look up fish at Dictionary.com
Old English fisc, from Proto-Germanic *fiskaz (cognates: Old Saxon, Old Frisian, Old High German fisc, Old Norse fiskr, Middle Dutch visc, Dutch vis, German Fisch, Gothic fisks), from PIE *peisk- "fish" (cognates: Latin piscis, Irish iasc, and, via Latin, Italian pesce, French poisson, Spanish pez, Welsh pysgodyn, Breton pesk).

Fish story attested from 1819, from the tendency to exaggerate the size of the catch (or the one that got away). Figurative sense of fish out of water first recorded 1610s.
fish (v.) Look up fish at Dictionary.com
Old English fiscian (cognates: Old Norse fiska, Old High German fiscon, German fischen, Gothic fiskon), from the root of fish (n.). Related: Fished; fishing.
fish-hook Look up fish-hook at Dictionary.com
late 14c., from fish (n.) + hook (n.).
fisher (n.) Look up fisher at Dictionary.com
Old English fiscere, agent noun from fish (v.). It began to be used of certain animals, hence perhaps the rise of the formation fisherman (1520s).
fishery (n.) Look up fishery at Dictionary.com
"business of fishing," 1670s; "place where fish are caught," 1690s; see fish (v.) + -ery. Related: Fisheries.
fishing (n.) Look up fishing at Dictionary.com
verbal noun from fish (v.), c.1300, fysschynge; figurative use from 1540s. Fishing rod (1550s) is older than fishing pole (1791). To "go fishing" is as old as Old English on fiscoð gan.
[O]f all diversions which ingenuity ever devised for the relief of idleness, fishing is the worst qualified to amuse a man who is at once indolent and impatient. [Scott, "Waverly," 1814]
fishmonger (n.) Look up fishmonger at Dictionary.com
mid-15c., from fish (n.) + monger (n.).
fishtail (n.) Look up fishtail at Dictionary.com
1840, from fish (n.) + tail (n.). As a verb, 1927, originally of aircraft, later automobiles. Related: Fishtailed; fishtailing.
fishwife (n.) Look up fishwife at Dictionary.com
1520s, from fish (n.) + wife in the "woman" sense.
fishy (adj.) Look up fishy at Dictionary.com
late 15c., from fish (n.) + -y (2). Sense of "shady, questionable" is first recorded 1840, perhaps from the notion of "slipperiness," or of giving off a bad odor.
fisk (v.) Look up fisk at Dictionary.com
2002, an Internet argument tactic involving a reprinting of an article or blog post, interlarded with rebuttals and refutations, often intended to show the original is a sandpile of flawed facts, unfounded assertions, and logical fallacies. 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. Related: Fisked; fisking.
fissile (adj.) Look up fissile at Dictionary.com
1660s, from Latin fissilis "that which may be cleft or split," from fissus, past participle of findere (see fissure).
fission (n.) Look up fission at Dictionary.com
1841, "division of a cell or organism," from Latin fissionem (nominative fissio) "a breaking up, cleaving," from past participle stem of findere "to split" (see fissure). Cognate with Old English bitan "to bite." Nuclear physics sense is 1939. As a verb, from 1929.
fissure (n.) Look up fissure at Dictionary.com
c.1400, from Old French fissure (13c.) and directly from Latin fissura "a cleft," from root of findere "to split, cleave," from PIE *bhi-n-d-, from root *bheid- "to split" (cognates: Sanskrit bhinadmi "I cleave," Old High German bizzan "to bite," Old English bita "a piece bitten off, morsel," Old Norse beita "to hunt with dogs," beita "pasture, food").
fist (n.) Look up fist at Dictionary.com
Old English fyst, from West Germanic *fustiz (cognates: Old Saxon and Old High German fust, Old Frisian fest, Middle Dutch vuust, Dutch vuist, German Faust), from Proto-Germanic *fukhstiz, probably ultimately from PIE *penkwe- "five" (see five, and compare Old Church Slavonic pesti, Russian piasti "fist").
fistful (n.) Look up fistful at Dictionary.com
1610s, from fist (n.) + -ful.
fistic (adj.) Look up fistic at Dictionary.com
1806, from fist (n.) + -ic. Historically not considered proper English.
fisticuffs (n.) Look up fisticuffs at Dictionary.com
c.1600, from fist (n.) + cuff, perhaps in imitation of handiwork. Related: Fisticuff.
fistula (n.) Look up fistula at Dictionary.com
"long, narrow ulcer," late 14c., from Latin fistula "pipe; ulcer," of uncertain origin.
fit (n.1) Look up fit at Dictionary.com
1823, "the fitting of one thing to another," later (1831) "the way something fits." Originally "an adversary of equal power" (mid-13c.), obscure, possibly from Old English fitt "a conflict, a struggle" (see fit (n.2)).
fit (v.) Look up fit at Dictionary.com
"be suitable," probably from early 15c.; "to be the right shape," 1580s, from fit (adj.). Related: Fitted; fitting. Fitted sheets is attested from 1963.
fit (n.2) Look up fit at Dictionary.com
"paroxysm, sudden attack" (as of anger), 1540s, probably via Middle English sense of "painful, exciting experience" (early 14c.), from Old English fitt "conflict, struggle," of uncertain origin, with no clear cognates outside English. Perhaps ultimately cognate with fit (n.1) on notion of "to meet." Phrase by fits and starts first attested 1610s.
fit (adj.) Look up fit at Dictionary.com
"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). Related: Fitter; fittest. Survival of the fittest (1867) coined by H. Spencer.
fit (n.3) Look up fit at Dictionary.com
part of a poem, Old English fitt, of unknown origin.
fitful (adj.) Look up fitful at Dictionary.com
used once by Shakespeare ("Macbeth," 1605) in sense of "characterized by fits," then revived by Scott (1810) with a sense of "shifting, changing." From fit (n.2) + -ful. Related: Fitfully; fitfulness.
fitness (n.) Look up fitness at Dictionary.com
1570s, from fit (adj.) + -ness.
fitter (n.) Look up fitter at Dictionary.com
1650s, agent noun from fit (v.).
fitting Look up fitting at Dictionary.com
1530s (adj.); c.1600 (n.), from present participle of fit (v.).
fitz Look up fitz at Dictionary.com
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 (n.) Look up five at Dictionary.com
Old English fif, from Proto-Germanic *fimfe (cognates: Old Frisian and Old Saxon fif, Dutch vijf, Old Norse fimm, Old High German funf, Gothic fimf), from PIE *penkwe- (cognates: Sanskrit panca, Greek pente, Latin quinque, Old Church Slavonic peti, Lithuanian penke, Old Welsh pimp). The sound shift that removed the *-m- is a regular development involving Old English, Old Frisian, and Old Saxon (as in thought, from stem of think; couth from *kunthaz; us from *uns.

Slang five-finger discount "theft" is from 1966. Five o'clock shadow attested by 1937. The original five-year plan was 1928 in the U.S.S.R.
fivefold (adv.) Look up fivefold at Dictionary.com
Old English fiffeald; see five + -fold.
fiver (n.) Look up fiver at Dictionary.com
1843, "five-pound note," from five + -er.
fix (v.) Look up fix at Dictionary.com
late 14c., "set (one's eyes or mind) on something," probably from Old French *fixer, from fixe "fixed," from Latin fixus "fixed, fast, immovable, established, settled," past participle of figere "to fix, fasten," from PIE root *dhigw- "to stick, to fix."

Sense of "fasten, attach" is c.1400; that of "settle, assign" is pre-1500 and evolved into "adjust, arrange" (1660s), then "repair" (1737). Sense of "tamper with" (a fight, a jury, etc.) is 1790. As euphemism for "castrate a pet" it dates from 1930. Related: Fixed; fixedly (1590s); fixing.
fix (n.) Look up fix at Dictionary.com
"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).
fixable (adj.) Look up fixable at Dictionary.com
late 15c., from fix (v.) + -able.
fixate (v.) Look up fixate at Dictionary.com
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. Related: Fixated; fixating.
fixation (n.) Look up fixation at Dictionary.com
late 14c., fixacion, an alchemical word, from Medieval Latin fixationem (nominative fixatio), noun of action from past participle stem of Latin fixare, frequentative of figere "to fix" (see fix (v.)). Used in the Freudian sense since 1910.