Quell shows the same Norman respelling as queen and quick: Old English cwellan, rewritten with qu- by scribes trained in French. The word itself is thoroughly native, with relatives across Germanic — Old Norse kvelja, "to torment," German quälen, "to torture."
The original meaning was much stronger than the modern one. Old English cwellan meant to kill, to murder, to execute, and the related cwalu meant a violent death. The milder sense of suppressing or extinguishing something developed by about 1300, and reducing a people to subjection by the 1560s. Etymonline is careful to correct a common guess: quell is not an earlier form of kill, despite the resemblance, and the identification of the two is simply wrong. They are different words that have drifted toward each other.
quell (v.) Middle English quellen "to kill" (a person or animal), from Old English cwellan "to kill, cause to die; murder, execute," from Proto-Germanic *kwaljanan (source also of Old English cwelan "to die," cwalu "violent death;" Old Saxon quellian "to torture, kill;" Old Norse kvelja "to torment;" Middle Dutch quelen "to vex, tease, torment;" Old High German quellan "to suffer pain," German quälen "to torment, torture"), from PIE root *gwele- "to throw, reach," with extended sense "to pierce." The original sense is obsolete; the milder sense of "suppress, extinguish, cause to cease," developed by c. 1300; that of "reduce to peace or subjection" is by 1560s. Compare quail (v.). "The common identification of quell with kill (1), of which it is said to be the earlier form, is erroneous" [Century Dictionary]. Related: Quelled ; quelling .
quell 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