Online Etymology Dictionary

quinquennial (adj.): late 15c., "lasting five years," from Latin quinquennis "of five years, celebrated every fifth year," from quinque- "five" (see quinque-) + ending from biennial, etc. Meaning "happening once every five years" attested from c.1600. As a noun from 1895; earlier quinquennal (1610s).
quinsy (n.): "severe sore throat," late 14c., qwinaci, from Old French quinancie (Modern French esquinacie), from Late Latin cynanche, from Greek kynankhe "sore throat," also "dog collar," literally "dog-choking," from kyon (genitive kynos) "dog" (see canine) + ankhein "to strangle," cognate with Latin angere (see anger (v.)).
quint (n.): 1520s, "a tax of one-fifth," from Middle French quint, from Latin quintus "the fifth," ordinal to quinque "five" (see quinque-). Used in English of various groups of five since 17c. First attested 1935 as a shortening of quintuplet (American English; British English prefers quin); used originally of the Dionne quintuplets, born May 28, 1934, near Callander, Ontario, Canada.
quinta (n.): "country house, villa," 1754, from Spanish and Portuguese quinta, originally a farm and house let out for a rent of one-fifth of its produce, from Latin quintus "one fifth," related to quinque "five" (see quinque-).
quintain (n.): "target for tilting and jousting practice," c.1400 (in Anglo-Latin from mid-13c.), from Old French quintaine or directly from Medieval Latin quintana; perhaps from Latin quintana "of the fifth" (see quinque-), which as a noun meant "the business part of a camp," on the supposition that this was where military exercises were done [OED].
quintal (n.): "a weight of a hundred pounds," c.1400, from Old French quintal "hundredweight," and directly from Medieval Latin quintale, from Arabic quintar, from Late Greek kentenarion, from Latin centenarius "containing a hundred" (see centenary).
quintessence (n.): early 15c., in ancient and medieval philosophy, "pure essence, substance of which the heavenly bodies are composed," literally "fifth essence," from Middle French quinte essence (14c.), from Medieval Latin quinta essentia, from Latin quinta, fem. of quintus "fifth" (see quinque-) + essentia (see Parousia).

A loan-translation of Greek pempte ousia, the "ether" added by Aristotle to the four known elements (water, earth, fire, air) and said to permeate all things. Its extraction was one of the chief goals of alchemy. Sense of "purest essence" (of a situation, character, etc.) is first recorded 1580s.
quintessential (adj.): c.1600, "purest, most refined," from quintessence (Medieval Latin quint essentia) + -al (1). Related: Quintessentially.
quintet (n.): 1811, "composition for five voices," from Italian quintetto, diminutive of quinto "fifth," from Latin quintus "the fifth," related to quinque "five" (see quinque-). Meaning "set of five singers or players" is from 1882.
quintile (n.): 1610s, originally in astrology, from Latin quintus "the fifth" (see quinque-) + -ile, from quartile. Use in statistics dates to 1951.
quintillion (n.): 1670s, from Latin quintus "the fifth" (see quinque-) + ending from million. Cf. billion. In Great Britain, the fifth power of a million (1 followed by 30 zeroes); in U.S. the sixth power of a thousand (1 followed by 18 zeroes).
quintuple (adj.): 1560s, from French quintuple (15c.), from Late Latin quintuplex, from Latin quintus "fifth" (related to quinque "five;" see quinque-) on model of quadruple. Related: Quintuplicate.
quintuple (v.): 1630s, from quintuple (adj.) or from French quintupler (v.). Related: Quintupled; quintupling.
quintuplet (n.): 1873, "set of five things" (originally in music), from quintuple (adj.) with ending from triplet. In plural, "five children at one birth" it is recorded from 1889.
quinzane (n.): "group of fifteen," 1856, from French quinzaine (12c.), from quinze "fifteen," from Latin quindecim (see fifteen).
quip (n.): 1530s, variant of quippy in same sense (1510s), perhaps from Latin quippe "indeed, of course, as you see, naturally, obviously" (used sarcastically), from quid "what" (neuter of pronoun quis "who;" see who), and cf. quibble (n.)) + emphatic particle -pe.
quip (v.): "make a quip," 1570s, from quip (n.). Related: Quipped; quipping.
quipu (n.): ancient Inca recording device using knotted cords, 1704, from Quechua quipu "knot."
quire (n.1): c.1200, "set of four folded pages for a book; pamphlet consisting of a single quire," from Anglo-French quier, Old French quaier "sheet of paper folded in four," from Vulgar Latin *quaternus, from Latin quaterni "four each," from quater "four times." Meaning "standard unit for selling paper" first recorded late 14c. In quires (late 15c.) means "unbound."
quire (n.2): early form and later variant spelling of choir (q.v.).
Quirinal: royal palace in Rome, 1838, from Mons Quirinalis in Rome (one of the seven hills, site of a former Papal palace), from Quirinus, said to be the divine name of Romulus, but really one of the original trinity of Roman gods, representing Mars. His feast (Quirinalia) was Feb. 17. Used metonymically for "the Italian civil government" (1917), especially as distinguished from the Vatican.
quirk (n.): 1560s, "quibble, evasion," of unknown origin, perhaps connected to German quer (see queer (adj.)) via notion of twisting and slanting; but its earliest appearance in western England dialect seems to argue against this source. Perhaps originally a technical term for a twist or flourish in weaving. Sense of "peculiarity" is c.1600.
quirky (adj.): 1806, "shifty," from quirk + -y (2). Sense of "idiosyncratic" first recorded 1960. Related: Quirkily; quirkiness.
quirt (n.): "short-handled braided leather riding whip," 1845, from Mexican Spanish cuarta "rope," related to Spanish cuerda "rope," from Latin corda (see cord (n.)).
quisling (n.): 1940, from Vidkun Quisling (1887-1945), Norwegian fascist politician who headed the puppet government during the German occupation of Norway in World War II; shot for treason after German defeat. First used in London Times of April 15, 1940, in a Swedish context.
quit (v.): c.1200, "to repay, discharge" (a debt, etc.), from Old French quiter "clear, establish one's innocence;" also transitive, "release, let go, relinquish, abandon" (12c.), from quite (see quit (adj.)).

Meaning "to reward, give reward" is mid-13c., that of "take revenge; to answer, retort" and "to acquit oneself" are late 14c. From c.1300 as "to acquit (of a charge), declare not guilty." Sense of "leave, depart" is attested from c.1400; that of "stop" (doing something) is from 1640s. Meaning "to give up, relinquish" is from mid-15c. Related: Quitted; quitting. Quitting time is from 1835.
quit (adj.): c.1200, "free, clear" (of debt, etc.), from Old French quite, quitte "free, clear, entire, at liberty; discharged; unmarried," from Medieval Latin quitus, quittus, from Latin quietus "free" (in Medieval Latin "free from war, debts, etc."), also "calm, resting" (see quiet (adj.)).
quit-rent (n.): early 15c., "rent paid by a tenant in exchange for being discharged from required service;" also, "nominal rent as acknowledgment of tenure," from quit (adj.) + rent (n.).
quitclaim (n.): "a relinquishing of a legal right or claim," c.1300, from Anglo-French quiteclame; see quit (v.) + claim (n.). Cf. Old French clamer quitte "to give up (a right)."
quite (adv.): early 14c., adverbial form of Middle English quit, quite (adj.) "free, clear" (see quit (adj.)). Originally "thoroughly;" the weaker sense of "fairly" is attested from mid-19c.
quits (adj.): "even" (with another), 1660s; earlier "discharged of a liability" (c.1200), perhaps from Medieval Latin quittus (see quit (adj.)).
quittance (n.): c.1200, "payment, compensation;" c.1300, "discharge from an obligation," from Old French quitance (Modern French quittance), from quiter (see quit (v.)).
quitter (n.): as an insult, 1881, American English, agent noun from quit (v.).
quiver (v.): "to tremble," late 15c., perhaps imitative, or possibly an alteration of quaveren (see quaver), or from Old English cwifer- (in cwiferlice "zealously"), which is perhaps related to cwic "alive" (see quick). Related: Quivered; quivering. As a noun in this sense from 1715, from the verb.
quiver (n.): "case for holding arrows," early 14c., from Anglo-French quiveir, Old French quivre, cuivre, probably of Germanic origin, from Proto-Germanic *kukur "container" (cf. Old High German kohhari, German Köcher, Old Saxon kokar, Old Frisian koker, Old English cocur "quiver"); "said to be from the language of the Huns" [Barnhart]. Related: Quiverful.
quixotic (adj.): "extravagantly chivalrous," 1791, from Don Quixote, romantic, impractical hero of Cervantes' satirical novel "Don Quixote de la Mancha" (1605; English translation by 1620). His name literally means "thigh," also "a cuisse" (a piece of armor for the thigh), in Modern Spanish quijote, from Latin coxa "hip." Related: Quixotical; quixotically.
quiz (n.): 1867, "brief examination of a student on some subject," perhaps from quiz (v.), or from apparently unrelated slang word quiz "odd person" (1782, source of quizzical). According to OED, the anecdote that credits this word to a bet by the Dublin theater-manager Daly or Daley that he could coin a word is regarded by authorities as "doubtful" and the first record of it appears to be in 1836 (in Smart's "Walker Remodelled"; the story is omitted in the edition of 1840).
quiz (v.): 1847, "to question," quies, perhaps from Latin qui es? "who are you?," first question in oral exams in Latin in old-time grammar schools. Spelling quiz first recorded 1886, though it was in use as a noun spelling from 1867, perhaps in this case from apparently unrelated slang word quiz "odd person" (1782, source of quizzical). Cf. quisby "queer, not quite right; bankrupt" (slang from 1807). From the era of radio quiz shows comes quizzee (n.), 1940.
quizzical (adj.): 1789, from quiz "odd or eccentric person" (1782), of unknown origin (see quiz (n.)) + -ical. Related: Quizzically.
quo warranto: Medieval Latin, literally "by what warrant," from quo "from, with, or by whom or what?," ablative of interrogative pronoun quis "who?" (see who).
quod: "prison," c.1700, a cant slang word of unknown origin; perhaps a variant of quad in the "building quadrangle" sense.
quodlibet (n.): "a nicety, subtlety," late 14c., Latin, literally "what you will, what you please," from quod "what," neuter of qui (see who) + libet "it pleases" (see love (n.)).
quoin (n.): 1530s, "a cornerstone," variant spelling of coin (n.); in early use also in other senses of that word, including "a wedge."
quoit (n.): late 14c., "curling stone," of uncertain origin, perhaps from Old French coite "flat stone" (with which the game was originally played), literally "cushion," variant of coilte (see quilt (n.)). Quoits were among the games prohibited by Edward III and Richard II to encourage archery. In reference to a heavy flat iron ring (and the tossing game played with it) it is recorded from mid-15c.
quoits (n.): late 14c., coytes "game played by throwing quoits;" see quoit.
quondam (adj.): "one-time, former," 1580s, from earlier use as an adverb ("formerly") and a noun ("former holder" of some office or position), both 1530s, from Latin quondam (adv.) "formerly, at some time, at one time; once in a while," from quom, cum "when, as" (see who) + demonstrative ending -dam.
Quonset hut: 1942, from Quonset Point Naval Air Station, Rhode Island, where this type of structure was first built, 1941. The place name is from a southern New England Algonquian language and perhaps means "small, long place."
quorate (adj.): "attended by a quorum," 1969, from quorum + -ate (1).
quorum (n.): early 15c., in reference to certain eminent justices of the peace, from Latin quorum "of whom," genitive plural (masc. and neuter; fem. quarum) of qui "who" (see who). The traditional wording of the commission appointing justices of the peace translates as, "We have also assigned you, and every two or more of you (of whom [quoram vos] any one of you the aforesaid A, B, C, D, etc. we will shall be one) our justices to inquire the truth more fully." The justices so-named usually were called the justices of the quorum. Meaning "fixed number of members whose presence is necessary to transact business" is first recorded 1610s.
quota (n.): 1660s, from Medieval Latin quota, from Latin quota pars "how large a part," from quota, fem. singular of quotus "which, what number (in sequence);" see quote (v.). Earliest reference is to contributions of soldiers or supplies levied from a town or district; immigration sense is from 1921.