factitive (adj.) Look up factitive at Dictionary.com
"causative, expressive of making or causing," 1813, from Latin factus, past participle of facere "to make, do" (see factitious) + -ive.
factoid (n.) Look up factoid at Dictionary.com
1973, "published statement taken to be a fact because of its appearance in print," from fact + -oid, first explained, if not coined, by Norman Mailer.
Factoids ... that is, facts which have no existence before appearing in a magazine or newspaper, creations which are not so much lies as a product to manipulate emotion in the Silent Majority. [Mailer, "Marilyn," 1973]
By 1988 it was being used in the sense of "small, isolated bit of true factual information."
factor (n.) Look up factor at Dictionary.com
early 15c., "commercial agent, deputy, one who buys or sells for another," from Middle French facteur "agent, representative" (Old French factor, faitor "doer, author, creator"), from Latin factor "doer, maker, performer," in Medieval Latin, "agent," agent noun from past participle stem of facere "to do" (see factitious). In commerce, especially "a commission merchant." Mathematical sense is from 1670s. Sense of "circumstance producing a result" is attested by 1816, from the mathematical sense.
factor (v.) Look up factor at Dictionary.com
1610s, "act as an agent, manage," from factor (n.). The use in mathematics is attested from 1837. Related: Factored; factoring.
factorial (n.) Look up factorial at Dictionary.com
1816, in mathematics, from factor + -al (2). As an adjective from 1837 in mathematics; from 1881 as "pertaining to a factor."
factory (n.) Look up factory at Dictionary.com
1550s, "estate manager's office," from Middle French factorie (15c.), from Late Latin factorium "office for agents ('factors')," also "oil press, mill," from Latin factor "doer, maker" (see factor (n.)). From 1580s as "establishment of merchants and factors in a foreign place." Sense of "building for making goods" is first attested 1610s. Factory farm attested from 1890.
factotum (n.) Look up factotum at Dictionary.com
"one who does all kinds of work for another," 1560s, from Medieval Latin factotum "do everything," from fac, imperative of facere "to make, do" (see factitious) + totum "all" (see total (adj.)).
factual (adj.) Look up factual at Dictionary.com
1834, formed from fact on model of actual. Related: Factually.
faculties (n.) Look up faculties at Dictionary.com
"powers or properties of one's mind," also "physical functions," early 16c., plural of faculty.
faculty (n.) Look up faculty at Dictionary.com
late 14c., "ability, opportunity, means, resources," from Old French faculte "skill, accomplishment, learning" (14c., Modern French faculté) and directly from Latin facultatem (nominative facultas) "power, ability, capability, opportunity; sufficient number, abundance, wealth," from *facli-tat-s, from facilis (see facile).

Academic sense "branch of knowledge" (late 14c.) was in Old French and probably was the earliest in English (it is attested in Anglo-Latin from late 12c.), on notion of "ability in knowledge" or "body of persons on whom are conferred specific professional powers." Originally each department was a faculty; the use in reference to the whole teaching staff of an entire college dates from 1767. Related: Facultative. The Latin words facultas and facilitas "were originally different forms of the same word; the latter, owing to its more obvious relationship to the adj., retained the primary sense of 'easiness', which the former had ceased to have before the classical period." [OED]
fad (n.) Look up fad at Dictionary.com
1834, "hobby, pet project" (adjective faddy is from 1824), of uncertain origin. Perhaps shortened from fiddle-faddle. Or perhaps from French fadaise "trifle, nonsense," which is ultimately from Latin fatuus "stupid." From 1881 as "fashion, craze," or as Century Dictionary has it, "trivial fancy adopted and pursued for a time with irrational zeal."
faddish (adj.) Look up faddish at Dictionary.com
1855, from fad + -ish. Related: Faddishness.
faddle (v.) Look up faddle at Dictionary.com
"to make much of a child," 1680s. Related: Faddled; faddling.
fade (v.) Look up fade at Dictionary.com
early 14c., "lose brightness, grow pale," from Old French fader "become weak, wilt, wither," from fade (adj.) "pale, weak; insipid, tasteless" (12c.), probably from Vulgar Latin *fatidus, which is said to be a blending of Latin fatuus "silly, tasteless" and vapidus "flat, flavorless." Related: Faded; fading. Of sounds, by 1819. Transitive sense from 1590s; in cinematography from 1918.
Adieu! adieu! thy plaintive anthem fades
Past the near meadows, over the still stream,
Up the hill-side; and now 'tis buried deep
In the next valley-glades:
Was it a vision, or a waking dream?
Fled is that music:--Do I wake or sleep?

[Keats, "Ode to a Nightingale"]
fade (n.) Look up fade at Dictionary.com
early 14c., "loss of freshness or vigor," from fade (adj.), c. 1300, " lacking in brilliance; pale, discolored, dull," from Old French fade (see fade (v.)). As a type of tapering hairstyle from 1988 (fade-out style is in a 1985 "Ebony" article on men's haircuts).
fade-out (n.) Look up fade-out at Dictionary.com
1918, from verbal phrase, from fade (v.) + out (adv.).
fader (n.) Look up fader at Dictionary.com
sound control device, 1931, agent noun from fade (v.).
fado (n.) Look up fado at Dictionary.com
popular music style of Portugal, 1902, from Latin fatum "fate, destiny" (see fate (n.)). Because the songs tell the fates of their subjects.
fadoodle (n.) Look up fadoodle at Dictionary.com
"something worthless or foolish," 1660s.
faecal (adj.) Look up faecal at Dictionary.com
see fecal.
faeces (n.) Look up faeces at Dictionary.com
see feces.
faerie (n.) Look up faerie at Dictionary.com
supernatural kingdom, "Elfland," c. 1300, from Old French fairie; see fairy.
faery Look up faery at Dictionary.com
see faerie.
fag (v.1) Look up fag at Dictionary.com
"to droop, decline in strength, become weary" (intransitive), 1520s, of uncertain origin; OED is content with the "common view" that it is an alteration of flag (v.) in its sense of "droop, go limp." Transitive sense of "to make (someone or something) fatigued, tire by labor" is first attested 1826. Related: Fagged; fagging.
fag (n.1) Look up fag at Dictionary.com
British slang for "cigarette" (originally, especially, the butt of a smoked cigarette), 1888, probably from fag "loose piece, last remnant of cloth" (late 14c., as in fag-end "extreme end, loose piece," 1610s), which perhaps is related to fag (v.), which could make it a variant of flag (v.).
fag (v.2) Look up fag at Dictionary.com
"put to work at certain duties, compel to work for one's benefit," 1806, from British public school slang fag (n.) "junior student who does certain duties for a senior" (1785), from fag (v.1). Related: Fagdom (1902); faggery "fatiguing labor" (1853).
fag (n.2) Look up fag at Dictionary.com
shortening of faggot (n.2) "male homosexual," by 1921. Fag hag "heterosexual woman who keeps company with gay men" attested by 1969.
faggot (n.1) Look up faggot at Dictionary.com
late 13c., "bundle of twigs bound up," also fagald, faggald, from Old French fagot "bundle of sticks" (13c.), of uncertain origin, probably from Italian faggotto "bundle of sticks," diminutive of Vulgar Latin *facus, from Latin fascis "bundle of wood" (see fasces).

Especially used for burning heretics (emblematic of this from 1550s), so that phrase fire and faggot was used to indicate "punishment of a heretic." Heretics who recanted were required to wear an embroidered figure of a faggot on the sleeve as an emblem and reminder of what they deserved.
faggot (n.2) Look up faggot at Dictionary.com
"male homosexual," 1914, American English slang, probably from earlier contemptuous term for "woman" (1590s), especially an old and unpleasant one, in reference to faggot (n.1) "bundle of sticks," as something awkward that has to be carried (compare baggage "worthless woman," 1590s). It may also be reinforced by Yiddish faygele "homosexual" (n.), literally "little bird." It also may have roots in British public school slang noun fag "a junior who does certain duties for a senior" (1785), with suggestions of "catamite," from fag (v.). This also spun off a verb (see fag (v.2).
He [the prefect] used to fag me to blow the chapel organ for him. ["Boy's Own Paper," 1889]
Other obsolete British senses of faggot were "man hired into military service merely to fill out the ranks at muster" (1700) and "vote manufactured for party purposes" (1817).

The explanation that male homosexuals were called faggots because they were burned at the stake as punishment is an etymological urban legend. Burning sometimes was a punishment meted out to homosexuals in Christian Europe (on the suggestion of the Biblical fate of Sodom and Gomorrah), but in England, where parliament had made homosexuality a capital offense in 1533, hanging was the method prescribed. Use of faggot in connection with public executions had long been obscure English historical trivia by the time the word began to be used for "male homosexual" in 20th century American slang, whereas the contemptuous slang word for "woman" (in common with the other possible sources or influences listed here) was in active use early 20c., by D.H. Lawrence and James Joyce, among others.
Fagin (n.) Look up Fagin at Dictionary.com
character in "Oliver Twist" (1838); used for "trainer of thieves" by 1842.
fagot (n.) Look up fagot at Dictionary.com
early alternative spelling of faggot (n.1).
fagoting (n.) Look up fagoting at Dictionary.com
in embroidery, 1885, from faggot (n.1) "bundle." So called from the threads tied together in the middle.
fagus (n.) Look up fagus at Dictionary.com
botanical genus of beech trees, from Latin fagus "beech," from PIE root *bhagos "beech tree" (source also of Greek phegos "oak," Latin fagus "beech," Russian buzina "elder," Old English bece, Old Norse bok, German Buche "beech"), perhaps with a ground sense of "edible" (and connected with the root of Greek phagein "to eat;" see -phagous). Beech mast was an ancient food source for agricultural animals across a wide stretch of Europe.
The restriction to western IE languages and the reference to different trees have suggested to some scholars that this word was not PIE, but a later loanword. In the Balkans, from which the beech started to spread after 6000 BC, the [Greek] word means 'oak,' not 'beech.' Yet 'oak' and 'beech' are both 'fruit-bearing trees,' so that a semantic shift from 'oak' to 'beech' appears quite conceivable. The word itself may then have been PIE after all. [de Vaan]
Fahrenheit (adj.) Look up Fahrenheit at Dictionary.com
temperature scale, 1753, named for Gabriel Daniel Fahrenheit (1686-1736), Prussian physicist who proposed the scale in 1714. The "zero" in it is arbitrary, based on the lowest temperature observed by him during the winter of 1709 in Danzig. An abstract surname meaning literally "experience."
faience (n.) Look up faience at Dictionary.com
fine kind of pottery or earthenware, 1714, from French faïence (16c.), probably from Fayence, French form of Faenza, city in Italy that was a noted ceramics center 16c. The city name is Latin faventia, literally "silence, meditation," perhaps a reference to a tranquil location.
fail (v.) Look up fail at Dictionary.com
c. 1200, "be unsuccessful in accomplishing a purpose;" also "cease to exist or to function, come to an end;" early 13c. as "fail in expectation or performance," from Old French falir "be lacking, miss, not succeed; run out, come to an end; err, make a mistake; be dying; let down, disappoint" (11c., Modern French faillir), from Vulgar Latin *fallire, from Latin fallere "to trip, cause to fall;" figuratively "to deceive, trick, dupe, cheat, elude; fail, be lacking or defective." Related: Failed; failing.

Replaced Old English abreoðan. From c. 1200 as "be unsuccessful in accomplishing a purpose;" also "cease to exist or to function, come to an end;" early 13c. as "fail in expectation or performance." From mid-13c. of food, goods, etc., "to run short in supply, be used up;" from c. 1300 of crops, seeds, land. From c. 1300 of strength, spirits, courage, etc., "suffer loss of vigor; grow feeble;" from mid-14c. of persons. From late 14c. of material objects, "break down, go to pieces."
fail (n.) Look up fail at Dictionary.com
late 13c., "failure, deficiency" (as in without fail), from Old French faile "deficiency," from falir (see fail (v.)). The Anglo-French form of the verb, failer, also came to be used as a noun, hence failure.
fail-safe (adj.) Look up fail-safe at Dictionary.com
also failsafe, fail safe "safe against failure," 1945, originally in reference to aircraft construction, from fail (v.) + safe (adj.). The novel about a nuclear attack caused by mechanical error is from 1962.
failing (n.) Look up failing at Dictionary.com
late 14c., "failure;" 1580s, "defect, fault," verbal noun from fail (v.).
failure (n.) Look up failure at Dictionary.com
1640s, failer, "a failing, deficiency," also "act of failing," from Anglo-French failer, Old French falir "be lacking; not succeed" (see fail (v.)). The verb in Anglo-French used as a noun; ending altered 17c. in English to conform with words in -ure. Meaning "thing or person considered as a failure" is from 1837.
fain (adj.) Look up fain at Dictionary.com
Old English fægen, fagen "glad, cheerful, happy, joyful, rejoicing," from a common Germanic root (cognates: Old Saxon fagan, Old Norse feginn "glad," Old High German faginon, Gothic faginon "to rejoice"), perhaps from PIE *pek- (1) "to make pretty." Often "glad" in a relative sense, "content to accept when something better is unobtainable." As an adverb, from c. 1200. Related: Fainly.
faineant (adj.) Look up faineant at Dictionary.com
1855; earlier as a noun (1610s); from French fainéant (16c.) "do-nothing," from fait, third person singular of faire "to do" (from Latin facere "to make, do;" see factitious) + néant "nothing" (compare dolce far niente). According to OED this is a French folk-etymology alteration of Old French faignant (14c.), present participle of faindre "to feign" (see feign). Applied in French to the late Merovingian kings, puppets in the hands of the palace mayors. Related: Faineance "the habit of doing nothing."
faint (adj.) Look up faint at Dictionary.com
c. 1300, "enfeebled; wearied, exhausted," from Old French faint, feint "false, deceitful; sham, artificial; weak, faint, lazy, indolent, cowardly," past participle of feindre "hesitate, falter, be indolent, show weakness, avoid one's duty by pretending" (see feign). Also from c. 1300 as "deceitful; unreliable; false." Meaning "wanting in spirit or courage, cowardly" (a sense now mostly encountered in faint-hearted) is from early 14c. From early 15c. of actions, functions, colors, etc., "weak, feeble, poor." Meaning "producing a feeble impression upon the senses" is from 1650s.
faint (v.) Look up faint at Dictionary.com
c. 1300, "grow weak, become enfeebled," also "lack courage or spirit, be faint-hearted," and "to pretend, feign;" from faint (adj.). Sense of "swoon, lose consciousness" is from c. 1400. Also used in Middle English of the fading of colors, flowers, etc. Related: Fainted; fainting. For Chaucer and Shakespeare, also a transitive verb ("It faints me").
faint (n.) Look up faint at Dictionary.com
c. 1300, "faintness, faint-heartedness," from faint (adj.). From 1808 as "a swoon."
faint-hearted (adj.) Look up faint-hearted at Dictionary.com
"cowardly, timorous," c. 1400, from faint (adj.) + hearted. Related: Faint-heartedly; faint-heartedness; faint-heart.
faintish (adj.) Look up faintish at Dictionary.com
1660s, from faint (adj.) + -ish.
faintly (adv.) Look up faintly at Dictionary.com
c. 1300, "dispiritedly, timidly, half-heartedly;" early 14c. "feebly, wearily, without vigor;" from faint (adj.) + -ly (2). Meaning "indistinctly" is from 1580s. Also in Middle English, "deceitfully, hypocritically, falsely" (mid-14c.).
faintness (n.) Look up faintness at Dictionary.com
early 14c., "feebleness, weariness," from faint (adj.) + -ness. Meaning "exhaustion" is mid-15c. Of color, light, etc., from 1640s.
fair (adj.) Look up fair at Dictionary.com
Old English fæger "pleasing to the sight (of persons and body features, also of objects, places, etc.); beautiful, handsome, attractive," of weather, "bright, clear, pleasant; not rainy," also in late Old English "morally good," from Proto-Germanic *fagraz (source also of Old Saxon fagar, Old Norse fagr, Swedish fager, Old High German fagar "beautiful," Gothic fagrs "fit"), perhaps from PIE *pek- (1) "to make pretty" (source also of Lithuanian puošiu "I decorate").

The meaning in reference to weather preserves the oldest sense "suitable, agreeable" (opposed to foul (adj.)). Of the main modern senses of the word, that of "light of complexion or color of hair and eyes, not dusky or sallow" (of persons) is from c. 1200, faire, contrasted to browne and reflecting tastes in beauty. From early 13c. as "according with propriety; according with justice," hence "equitable, impartial, just, free from bias" (mid-14c.).

Of wind, "not excessive; favorable for a ship's passage," from late 14c. Of handwriting from 1690s. From c. 1300 as "promising good fortune, auspicious." Also from c. 1300 as "above average, considerable, sizable." From 1860 as "comparatively good."

The sporting senses (fair ball, fair catch, etc.) began to appear in 1856. Fair play is from 1590s but not originally in sports. Fair-haired in the figurative sense of "darling, favorite" is from 1909. First record of fair-weather friends is from 1736 (in a letter from Pope published that year, written in 1730). The fair sex "women" is from 1660s, from the "beautiful" sense (fair as a noun meaning "a woman" is from early 15c.). Fair game "legitimate target" is from 1776, from hunting.
Others, who have not gone to such a height of audacious wickedness, have yet considered common prostitutes as fair game, which they might pursue without restraint. ["Advice from a Father to a Son, Just Entered into the Army and about to Go Abroad into Action," London, 1776]