c. 1200, "to strike, hit, beat, knock;" c. 1300, "to deprive of life, put to death;" perhaps from an unrecorded variant of Old English cwellan "to kill, 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." Related: Killed; killing. Meaning "nullify or neutralize the qualities of" is from 1610s. Of time, 1728; of engines 1886; of lights, 1934. Kill-devil, colloquial for "rum," especially if new or of bad quality, is from 1630s. Dressed to kill first attested 1818 in a letter of Keats (compare killing (adj.) in the sense "overpowering, fascinating, attractive").
"stream, creek," 1630s, American English, from Dutch kil "a channel," from Middle Dutch kille "riverbed, inlet." The word is preserved in place names in the Mid-Atlantic American states (such as Schuylkill, Catskill, Fresh Kills, etc.). A common Germanic word, the Old Norse form, kill, meant "bay, gulf" and gave its name to Kiel Fjord on the Baltic coast and thence to Kiel, the German port city founded there in 1240.
early 13c., "a stroke, a blow," from kill (v.). Meaning "the act of killing" is from 1814 in hunting slang; that of "a killed animal" is from 1878. Lawn tennis serve sense is from 1903. The kill "the knockout" is boxing jargon, 1950. Kill ratio is from 1968, American English.