quantum (n.)youdaoicibaDictYouDict[quantum 词源字典]
1610s, "one's share or portion," from Latin quantum (plural quanta) "as much as, so much as; how much? how far? how great an extent?" neuter singular of correlative pronominal adjective quantus "as much" (see quantity). Introduced in physics directly from Latin by Max Planck, 1900; reinforced by Einstein, 1905. Quantum theory is from 1912; quantum mechanics, 1922; quantum jump is first recorded 1954; quantum leap, 1963, often figurative.[quantum etymology, quantum origin, 英语词源]
quarantine (n.)youdaoicibaDictYouDict
1520s, "period of 40 days in which a widow has the right to remain in her dead husband's house." Earlier quarentyne (15c.), "desert in which Christ fasted for 40 days," from Latin quadraginta "forty," related to quattuor "four" (see four).

Sense of "period a ship suspected of carrying disease is kept in isolation" is 1660s, from Italian quarantina giorni, literally "space of forty days," from quaranta "forty," from Latin quadraginta. So called from the Venetian custom of keeping ships from plague-stricken countries waiting off its port for 40 days (first enforced 1377) to assure that no latent cases were aboard. The extended sense of "any period of forced isolation" is from 1670s.
quarantine (v.)youdaoicibaDictYouDict
1804, from quarantine (n.). Related: Quarantined; quarantining.
quark (n.)youdaoicibaDictYouDict
1964, applied by U.S. physicist Murray Gell-Mann (b.1929), who said in correspondence with the editors of the OED in 1978 that he took it from a word in James Joyce's "Finnegans Wake" (1939), but also that the sound of the word was in his head before he encountered the printed form in Joyce. German Quark "curds, rubbish" has been proposed as the ultimate inspiration [Barnhart; Gell-Mann's parents were immigrants from Austria-Hungary]. George Zweig, Gell-Mann's co-proposer of the theory, is said to have preferred the name ace for them.
quarrel (n.1)youdaoicibaDictYouDict
"angry dispute," mid-14c., originally "ground for complaint," from Old French querele "matter, concern, business; dispute, controversy" (Modern French querelle), from Latin querella "complaint, accusation; lamentation," from queri "to complain, lament." Replaced Old English sacan. Sense of "contention between persons" is from 1570s.
quarrel (n.2)youdaoicibaDictYouDict
"square-headed bolt for a crossbow," mid-13c., from Old French quarel, carrel "bolt, arrow," from Vulgar Latin *quadrellus, diminutive of Late Latin quadrus (adj.) "square," related to quattuor "four" (see four). Now-archaic sense of "square or diamond-shaped plane of glass" first recorded mid-15c.
quarrel (v.)youdaoicibaDictYouDict
late 14c., "to raise an objection;" 1520s as "to contend violently, to fall out," from quarrel (n.1) and in part from Old French quereler (Modern French quereller). Related: Quarrelled; quarrelling.
quarrelsome (adj.)youdaoicibaDictYouDict
1590s, from quarrel (n.1) + -some (1). Related: Quarrelsomeness.
quarry (n.1)youdaoicibaDictYouDict
"what is hunted," early 14c., quirre "entrails of deer placed on the hide and given to dogs of the chase as a reward," from Anglo-French quirreie, Old French cuiriee "the spoil, quarry" (Modern French curée), altered (by influence of Old French cuir "skin," from Latin corium "hide"), from Old French corée "viscera, entrails," from Vulgar Latin *corata "entrails," from Latin cor "heart," from PIE root *kerd- (1) "heart" (see heart (n.)). Sense of "anything chased in hunt" is first recorded 1610s; earlier "bird targeted by a hawk or other raptor" (late 15c.).
quarry (n.2)youdaoicibaDictYouDict
"open place where rocks are excavated," c. 1400 (mid-13c. as a place name), from Medieval Latin quareia, dissimilated from quarreria (mid-13c.), literally "place where stones are squared," from Latin quadrare "to square" (see quadrant).
quarry (v.)youdaoicibaDictYouDict
1774, from quarry (n.2). Related: Quarried; quarrying.
quarryman (n.)youdaoicibaDictYouDict
1610s, from quarry (n.2) + man (n.). Related: Quarrymen.
quart (n.)youdaoicibaDictYouDict
"one-fourth of a gallon," early 14c., from Old French quarte "a fourth part" (13c.), from Latin quarta (pars), from fem. of quartus "the fourth," related to quattuor "four," from PIE root *kewtwor- (see four). Compare Latin quartarius "fourth part," also the name of a small liquid measure (the fourth part of a sextarius), which was about the same as an English pint.
quarter (n.)youdaoicibaDictYouDict
c. 1300, "one-fourth of anything; one of four parts or divisions of a thing;" often in reference to the four parts into which a slaughtered animal is cut, from Old French quartier, cartier (12c.), from Latin quartarius "fourth part," from quartus "fourth" (see quart). One of the earliest dated references in English is to "parts of the body as dismembered during execution" (c. 1300).

Used of the phases of the moon from early 15c. The use of quarter of an hour is attested from mid-15c. In Middle English quarter also meant "one of the four divisions of a 12-hour night" (late 14c.), and the quarter of the night meant "nine o'clock p.m." (early 14c.).

From late 14c. as "one of the four quadrants of the heavens;" hence, from the notion of the winds, "a side, a direction" (c. 1400). In heraldry from mid-14c. as "one of the four divisions of a shield or coat of arms." The word's connection with "four" loosened in Middle English and by 15c. expressions such as six-quartered for "six-sided" are found. Meaning "region, locality, area, place" is from c. 1400. Meaning "portion of a town" (identified by the class or race of people who live there) is first attested 1520s. For military sense, see quarters. As a period of time in a football game, from 1911. Quarter horse, bred strong for racing on quarter-mile tracks, first recorded 1834.

The coin (one fourth of a dollar) is peculiar to U.S., first recorded 1783. But quarter could mean "a farthing" in Middle English (late 14c.), and compare British quadrant "a farthing" (c. 1600), and classical Latin quadrans, the name of a coin worth a quarter of an as (the basic unit of Roman currency).

Quarter days (mid-15c.), designated as days when rents were paid and contracts and leases began or expired, were, in England, Lady day (March 25), Midsummer day (June 24), Michaelmas day (Sept. 29), and Christmas day (Dec. 25); in Scotland, keeping closer to the pagan Celtic calendar, they were Candlemas (Feb. 2), Whitsunday (May 15), Lammas (Aug. 1), and Martinmas (Nov. 11). Quarter in the sense "period of three months; one of the four divisions of a year" is recorded from late 14c.
quarter (v.)youdaoicibaDictYouDict
"to cut in quarters, divide into four parts," mid-14c., from quarter (n.). Specifically as the word for a form of criminal punishment from late 14c. (Old English had slitcwealm "death by rending"). Related: Quartered; quartering. The meaning "to put up soldiers" is recorded from 1590s (see quarters).
quarterback (n.)youdaoicibaDictYouDict
in U.S. football, 1876, from quarter (n.) + back (n.); so called from his position on the field at the start of play, between the halfback and the center. As a verb from 1945. Figurative sense from 1952. Monday morning quarterback is 1932 (n.), 1972 (v.); originally pro football player slang for sportswriters (U.S. professional football games typically are played on Sundays).
quarterly (adv.)youdaoicibaDictYouDict
early 15c., from quarter (n.) + -ly (2). As an adjective from 1560s, from -ly (1). As a noun, from 1830, "a quarterly publication," from the adjective.
quartermaster (n.)youdaoicibaDictYouDict
early 15c., "subordinate officer of a ship," from French quartier-maître or directly from Dutch kwartier-meester; originally a ship's officer whose duties included stowing of the hold; later (c. 1600) an officer in charge of quarters and rations for troops. See quarters.
quarters (n.)youdaoicibaDictYouDict
"military dwelling place," 1590s, from quarter (n.) in sense of "portion of a town." As "part of an American plantation where the slaves live," from 1724. The military sense seems to be also the source of quartermaster and it might be behind the phrase give quarter "spare from immediate death" (1610s, often in the negative), on the notion of "provide a prisoner with shelter."
quarterstaff (n.)youdaoicibaDictYouDict
also quarter-staff, 1540s (quarter-stroke "stroke with a quarterstaff" is attested from early 15c.), stout pole, six to eight feet long (six-and-a-half sometimes is given as the standard length), tipped with iron, formerly a weapon used by the English peasantry. From staff (n.); the quarter is of uncertain signification. According to one theory, favored by fencing manuals, etc., it likely is in reference to operation of the weapon:
It was grasped by one hand in the middle, and by the other between the middle and the end. In the attack the latter hand shifted from one quarter of the staff to the other, giving the weapon a rapid circular motion, which brought the ends on the adversary at unexpected points. [Century Dictionary]
Linguists tend to prefer an explanation from woodcutting, perhaps a reference to a cut of lumber known as a quarter, but contemporary evidence is wanting for either conjecture.