Quick is Old English cwic, respelled qu- by Norman scribes — the same conversion that turned cwen into queen and cwellan into quell. Native word, French spelling.
Its meaning has moved entirely. Cwic meant living, alive, animate; the sense of speedy developed only around 1300, out of the idea of being full of life. The original sense survives in a handful of fossils: the quick and the dead, quicksilver for mercury because it moves as if alive, quicksand, and the quick of a fingernail, the living flesh beneath. Etymonline notes a fine distinction still detectable in modern usage: fast and swift can describe rapid motion of any duration, but quick keeps something of "sudden" or "soon over" — a fast runner, but a quick starter.
quick (adj.) Middle English quik , from Old English cwic "living, alive, animate, characterized by the presence of life" (now archaic), and figuratively, of mental qualities, "rapid, ready," from Proto-Germanic *kwikwaz (source also of Old Saxon and Old Frisian quik , Old Norse kvikr "living, alive," Dutch kwik "lively, bright, sprightly," Old High German quec "lively," German keck "bold"), from PIE root *gwei- "to live." Sense of "lively, active, swift, speedy, hasty," developed by c. 1300, on notion of "full of life." NE swift or the now more common fast may apply to rapid motion of any duration, while in quick (in accordance with its original sense of 'live, lively') there is a notion of 'sudden' or 'soon over.' We speak of a fast horse or runner in a race, a quick starter but not a quick horse. A somewhat similar feeling may distinguish NHG schnell and rasch or it may be more a matter of local preference. [Carl Darling Buck, "A Dictionary of Selected Synonyms in the Principal Indo-European Languages," 1949] Of persons, "mentally active, prompt to perceive or respond to impressions" from late 15c. Of an action, process, etc., "done in little time," 1540s. Also in Middle English used of soft soils, gravel pits, etc. where the ground is shifting and yielding (mid-14c., compare quicksand ). Also in Middle English "with child, in an advanced state of pregnancy" (when the woman can feel the child move within). Also formerly of bright flowers or colors (c. 1200). As an adverb, "quickly, in a quick manner," from c. 1300. To be quick about something is from 1937. Quick buck is from 1946, American English. Quick-change artist (1886) originally was an actor expert in playing different roles in the same performance of a show. Quick-witted is from 1520s. quick (n.) "living persons," Old English cwic , from quick (adj.). Frequently paired with the dead , from phrasing in the Nicene and Apostles' creeds, as in Middle English þan cwike and þa deaden , Old English cwicum & deadum . The quick "tender part of the flesh" (under a nail, etc.) is from late 14c. ( quick (adj.) in the extended sense of "sensitive to pain" is from c. 1200); the figurative use of it, in touch (someone) to the quick is from 1520s.
quick came in through Norman French, and its spelling follows that family's conventions.
How that family writes these sounds
| /kw/ | qu-, even in native words the scribes got hold of: queen was cwenqueen, quick, quell |
What gives it away on the page
| qu- where you'd expect cw- | Pure scribal respelling of native words: queen was cwen, quick was cwic.queen, quick, quell |
Norman French in the spelling guide · guess another word's family