Online Etymology Dictionary

fibril (n.): 1680s, Englishing of Modern Latin fibrilla "a little fiber, a filament," especially in botany, diminutive of Latin fibra "a fiber, filament" (see fiber). Latin fibra and fibrilla were used in 17c. physiology in English alongside nativized fibre and fibril. From 1931 as "thread-like molecular formation."
fibrillar (adj.): "pertaining to or of the nature of fibrillae," 1847, from fibrilla (see fibril) + -ar.
fibrillate (v.): 1798, "form into fibrils or fibers," from fibrilla (see fibril) + -ate (2). Related: Fibrillated; fibrillating.
fibrillation (n.): 1842, "state of being fibrillar" (that is, "arranged in fibrils"), noun of action from fibrillate (v.). Especially "a quavering in the fibrils of the muscles of the heart" causing irregular beating (1882).
fibrin (n.): blood-clotting substance, 1800, from Latin fibra "a fiber, filament" (see fiber) + chemical suffix -in (2). So called because it is deposited as a network of fibers that cause the blood to clot.
fibro-cartilage (n.): 1818, from comb. form of fiber + cartilage.
fibroid (adj.): 1848, from fiber + -oid.
fibromyalgia (n.): 1981, said to have been coined by U.S. rheumatologist Mohammed Yunus, from Latin fibra "a fiber, filament" (see fiber) + Greek mys (genitive myos) "muscle" (see muscle (n.)) + -algia "pain." The earlier name for the condition was fibrositis.
fibrosis (n.): "fibrous growth or development in an organ," 1871, a Modern Latin hybrid, from Latin fibra "a fiber, filament" (see fiber) + Greek suffix -osis.
fibrous (adj.): "consisting of, or having the characteristics of, fibers," 1620s, from Modern Latin fibrosus, from Latin fibra "a fiber, filament" (see fiber).
fibula (n.): 1670s, "clasp, buckle, brooch," from Latin fibula "clasp, brooch; bolt, peg, pin," related to figere "to drive in, insert, fasten" (see fix (v.)). In reference to brooches, the modern English word mostly is used in archaeology. As "smaller bone in the lower leg" from 1706, from a Latin loan-translation of Greek perone "small bone in the lower leg," originally "clasp, brooch; anything pointed for piercing or pinning;" the bone was so called because it resembles a clasp such as that found in a modern safety pin. Related: Fibular.
fiche (n.): 1949, "slip of paper, form," especially "the form filled in by foreign guests in French hotels" [OED], from French fiche "card, index card, slip, form" (15c.), verbal noun from Old French fichier "to attach, stick into, pin on" (12c.), from Vulgar Latin *figicare, from Latin figere "to fix, fasten" (see fix (v.)). Sense of "card, strip of film" is a shortening of microfiche (1950).
fichu (n.): "scarf, neckerchief, small, triangular piece forming part of a woman's dress," 1803, from French fichu (18c. in this sense), apparently a noun use of the adjective fichu "carelessly thrown on," from Latin figere "to fasten" (see fix (v.)). "[M]od. substitution for a coarser word" [Weekley].
fickle (adj.): c. 1200, "false, treacherous, deceptive, deceitful, crafty" (obsolete), probably from Old English ficol "deceitful, cunning, tricky," related to befician "deceive," and to facen "deceit, treachery; blemish, fault." Common Germanic (compare Old Saxon fekan "deceit," Old High German feihhan "deceit, fraud, treachery"), from PIE *peig- (2) "evil-minded, treacherous, hostile" (see foe).

Sense of "changeable, inconstant, unstable" is from c. 1300 (especially of Fortune and women). Related: Fickleness. Fickly (c. 1300) is rare or obsolete. Also with a verb form in Middle English, fikelen "to deceive, flatter," later "to puzzle, perplex," which survived long enough in Northern dialects to get into Scott's novels. Fikel-tonge (late 14c.) was an allegorical or character name for "one who speaks falsehoods."
fictile (adj.): 1620s, "molded or formed by art," from Latin fictilis "made of clay, earthen," from fictio "a fashioning" (see fiction). From 1670s as "capable of being molded." From 1854 as "pertaining to pottery." Related: Fictility.
fiction (n.): early 15c., ficcioun, "that which is invented or imagined in the mind," from Old French ficcion "dissimulation, ruse; invention, fabrication" (13c.) and directly from Latin fictionem (nominative fictio) "a fashioning or feigning," noun of action from past participle stem of fingere "to shape, form, devise, feign," originally "to knead, form out of clay," from PIE *dheigh- "to build, form, knead" (source also of Old English dag "dough;" see dough).

Meaning "prose works (not dramatic) of the imagination" is from 1590s, at first often including plays and poems. Narrower sense of "the part of literature comprising novels and short stories based on imagined scenes or characters" is by early 19c. The legal sense (fiction of law) is from 1580s. A writer of fiction could be a fictionist (1827). The related Latin words included the literal notion "worked by hand," as well as the figurative senses of "invented in the mind; artificial, not natural": Latin fictilis "made of clay, earthen;" fictor "molder, sculptor" (also borrowed 17c. in English), but also of Ulysses as "master of deceit;" fictum "a deception, falsehood; fiction."
fictional (adj.): "pertaining to fiction," 1833, from fiction + -al (1). Earlier fictitious also was used in this sense (1773).
fictionalization (n.): 1946, noun of action from fictionalize.
fictionalize (v.): 1911, from fictional + -ize. Related: Fictionalized; fictionalizing. Earlier was fictionize (1822).
fictitious (adj.): 1610s, "artificial, counterfeit;" 1620s, "existing only in imagination," from Medieval Latin fictitius, a misspelling of Latin ficticius "artificial, counterfeit," from fictus "feigned, fictitious, false," past participle of fingere "to shape, form, devise, feign" (see fiction). Related: Fictitiously; fictitiousness.
fictive (adj.): 1610s, "formed by imagination," from French fictif, from stem of Latin fictio (see fiction). Earlier as "convincingly deceptive" (late 15c.). Related: Fictively.
ficus (n.): c. 1400, from Latin ficus "fig, fig tree" (see fig). With capital letter, as the name of a large genus of trees and shrubs, chosen by Linnaeus (1753).
fiddle (n.): "stringed musical instrument, violin," late 14c., fedele, fydyll, fidel, earlier fithele, from Old English fiðele "fiddle," which is related to Old Norse fiðla, Middle Dutch vedele, Dutch vedel, Old High German fidula, German Fiedel "a fiddle;" all of uncertain origin.

The usual suggestion, based on resemblance in sound and sense, is that it is from Medieval Latin vitula "stringed instrument" (source of Old French viole, Italian viola), which perhaps is related to Latin vitularia "celebrate joyfully," from Vitula, Roman goddess of joy and victory, who probably, like her name, originated among the Sabines [Klein, Barnhart]. Unless the Medieval Latin word is from the Germanic ones.
FIDDLE, n. An instrument to tickle human ears by friction of a horse's tail on the entrails of a cat. [Ambrose Bierce, "The Cynic's Word Book," 1906]
Fiddle has been relegated to colloquial usage by its more proper cousin, violin, a process encouraged by phraseology such as fiddlesticks (1620s), contemptuous nonsense word fiddle-de-dee (1784), and fiddle-faddle. Century Dictionary reports that fiddle "in popular use carries with it a suggestion of contempt and ridicule." Fit as a fiddle is from 1610s.
fiddle (v.): late 14c., "play upon a fiddle," from fiddle (n.); the figurative sense of "to act nervously, make idle movements, move the hands or something held in them in an idle, ineffective way" is from 1520s. Related: Fiddled; fiddling.
fiddle-faddle: 1570s, "trifles" (n.); 1630s "busy oneself with trifles; talk nonsense" (v.), apparently a reduplication of obsolete faddle "to trifle," or of fiddle in its contemptuous sense.
fiddle-head (n.): also fiddlehead, "one with a head as hollow as a fiddle," 1854 (fiddleheaded), from fiddle (n.) + head (n.). As a name for young fern fronds, from 1877, from resemblance to a violin's scroll. Earliest use is nautical, "carved ornamental work at the bow of a ship in the form of a scroll or volute" (1799).
There are three kinds of heads,--1st The Figure-head is one on which is placed the figure of a man, woman, or the like, &c.; 2d, The Billet-head, or Scroll-head is one finished with two scrolls or volutes ...; and 3d, the Fiddle-head, which is finished with only one scroll or volute, having the spirals turning inwards to the vessel. [Peter Hedderwick, "Treatise on Marine Architecture," Edinburgh, 1830]
fiddler (n.): late 13c., from Old English fiðelere "fiddler" (fem. fiðelestre), agent noun from fiddle (v.). Similar formation in Dutch vedelaar, German Fiedler, Danish fidler. Fiddler's Green "sailor's paradise" first recorded 1825, nautical slang. Fiddler crab is from 1714.
fiddlestick (n.): 15c., originally "the bow of a fiddle," from fiddle (n.) and stick (n.). Meaning "nonsense" (usually fiddlesticks) is from 1620s. As an exclamation, c. 1600.
fideism (n.): in various theological doctrines making knowledge dependent on faith, 1885, from Latin fides "faith" (see faith) + -ism.
fidelity (n.): early 15c., "faithfulness, devotion," from Middle French fidélité (15c.), from Latin fidelitatem (nominative fidelitas) "faithfulness, adherence, trustiness," from fidelis "faithful, true, trusty, sincere," from fides "faith" (see faith). From 1530s as "faithful adherence to truth or reality;" specifically of sound reproduction from 1878.
fidget (n.): 1670s, as the fidget "uneasiness," later the fidgets, from a verb fidge "move restlessly" (16c., surviving longest in Scottish), perhaps from Middle English fiken "to fidget, hasten" (see fike (v.)).
fidget (v.): 1670s (implied in fidgetting); see fidget (n.). Related: Fidgeted.
fidgety (adj.): 1730s, from fidget (n.) + -y (2). Related: Fidgetiness.
fiducial (adj.): 1570s, "assumed as a fixed basis for comparison," from Latin fiducialis "reliable," from fiducia "trust" (see faith). From 1620s as "pertaining to trust;" 1832 as "fiduciary."
fiduciary (adj.): 1640s, "holding something in trust," from Latin fiduciarius "entrusted, held in trust," from fiducia "trust, confidence, reliance;" in law, "a deposit, pledge, security," from root of fidere "to trust" (see faith). In Roman law, fiducia was "a right transferred in trust;" paper currency sense (1878) is because its value depends on the trust of the public. As a noun, "one who holds something in trust," from 1630s.
fie (interj.): late 13c., possibly from Old French fi, exclamation of disapproval (12c.), and reinforced by Old Norse fy or some other Scandinavian form; it's a general sound of disgust that seems to have developed independently in many languages. Fie-fie was a 19c. British jocular word for "improper," also, as a noun, "woman of tarnished reputation" [OED].
fief (n.): also feoff, 1610s, from French fief (12c.) "a 'feud,' possession, holding, domain; feudal duties, payment," from Medieval Latin feodum "land or other property whose use is granted in return for service," widely said to be from Frankish *fehu-od "payment-estate," or a similar Germanic compound, in which the first element is from Proto-Germanic *fekhu, making it cognate with Old English feoh "money, movable property, cattle" (see fee). Second element perhaps is similar to Old English ead "wealth" (see Edith).
fiefdom (n.): 1814, from fief + -dom.
field (n.): Old English feld "plain, pasture, open land, cultivated land" (as opposed to woodland), also "a parcel of land marked off and used for pasture or tillage," probably related to Old English folde "earth, land," from Proto-Germanic *felthuz "flat land" (Cognates: Old Saxon and Old Frisian feld "field," Old Saxon folda "earth," Middle Dutch velt, Dutch veld Old High German felt, German Feld "field," but not found originally outside West Germanic; Swedish fält, Danish felt are borrowed from German; Finnish pelto "field" is believed to have been adapted from Proto-Germanic). This is from PIE *pel(e)-tu-, from root *pele- (2) "flat, to spread" (see plane (n.1)). The English spelling with -ie- probably is the work of Anglo-French scribes (compare brief, piece).

As "battle-ground," c. 1300. Meaning "sphere or range of any related things" is from mid-14c. Physics sense is from 1845. Collective use for "all engaged in a sport" (or, in horse-racing, all but the favorite) is 1742; play the field "avoid commitment" (1936) is from notion of gamblers betting on other horses than the favorite. Cricket and baseball sense of "ground on which the game is played" is from 1875. Sense of "tract of ground where something is obtained or extracted" is from 1859. As an adjective in Old English combinations, often with a sense of "rural, rustic" (feldcirice "country-church," feldlic "rural"). Of slaves, "assigned to work in the fields" (1817, in field-hand), opposed to house. A field-trial originally was of hunting dogs.
field (v.): "to go out to fight," 16c., from field (n.) in the specific sense of "battlefield" (Old English). The sports meaning "to stop and return the ball" is first recorded 1823, originally in cricket; figurative sense of this is from 1902. Related: Fielded; fielding.
field-book (n.): naturalist's notebook for observations in the field, 1848, from field (n.) + book (n.).
field-day (n.): 1747, originally a day of military exercise and review (see field (v.)); figurative sense "any day of unusual bustle, exertion, or display" [Century Dictionary] is from 1827.
field-glass (n.): magnifying apparatus, by 1836, so called from being used in the field; see field (n.) + glass (n.).
field-goal (n.): 1889 in football, from field (n.) + goal (n.). A score made from the playing field.
field-marshal (n.): high military rank in some European armies, 1610s, from field (n.) + marshal (n.). Compare French maréchal de camp, German Feldmarschall.
field-work (n.): 1767, "gathering statistics or doing research out-of-doors or on-site," from field (n.) + work (n.). From 1819 in reference to a type of military fortification raised by troops in the field.
fielder (n.): early 14c., "one who works in a field," agent noun from field (n.). Sporting sense is from 1832 (in cricket; by 1868 in baseball). Earlier in cricket was simply field (1825) and fieldsman (1767).
fielding (n.): "play in the field," 1823 in cricket (by 1884 in baseball), verbal noun from field (v.).
fieldstone (n.): stone found in fields, as used for buildings, 1797, from field (n.) + stone (n.).
fiend (n.): Old English feond "enemy, foe, adversary," originally present participle of feogan "to hate," from Proto-Germanic *fijand- "hating, hostile" (source also of Old Frisian fiand "enemy," Old Saxon fiond, Middle Dutch viant, Dutch vijand "enemy," Old Norse fjandi, Old High German fiant, Gothic fijands), from suffixed form of PIE root *pe(i)- "to hurt" (source also of Sanskrit pijati "reviles, scorns," Greek pema "suffering, misery, woe," Gothic faian "to blame," and possibly Latin pati "to suffer, endure"). According to Watkins, not allied to foe and feud (n.).

As spelling suggests, the word originally was the opposite of friend (n.). Both are from the active participles of the Germanic verbs for "to love" and "to hate." According to Bammesberger ["English Etymology"], "The long vowel in FIEND is regular. In FRIEND the vowel has been shortened; perhaps the shortening is due to compounds like FRIENDSHIP, in which the consonant group (-nds-) regularly caused shortening of the preceeding long vowel."

Fiend at first described any hostile enemy (male and female, with abstract noun form feondscipe "fiendship"), but it began to be used in late Old English for "the Devil, Satan" (literally "adversary") as the "enemy of mankind," which shifted its sense to "diabolical person" (early 13c.). The old sense of the word devolved to foe, then to the imported word enemy. For spelling with -ie- see field. Meaning "devotee (of whatever is indicated)," as in dope fiend, is from 1865.