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.
The meaning "to nullify or neutralize the qualities of" is attested from 1610s. Of time, from 1728; of engines, from 1886; of lights, from 1934. Kill-devil, colloquial for "rum," especially if new or of bad quality, is from 1630s. Dressed to kill is 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.
"act of slaying, "mid-15c., verbal noun from kill (v.). Meaning "large profit" is from 1886, American English slang.
mid-15c., "deadly, depriving of life," present-participle adjective from kill (v.). Meaning "overpowering, fascinating, attractive" is 1630s, from the verb in a figurative sense "overwhelm (someone) by strong effect on the mind or senses." Meaning "very powerful in effect, exceedingly severe, so as to (almost) kill one" is from 1844. Related: Killingly.
late 15c., agent noun from kill (v.). But a surname, Ric[hard] Le Kyller is attested from 1288. Figurative use from 1550s. Meaning "impressive person or thing" is by 1900 (as an adjective, 1979); reduplicated form killer-diller attested by 1938. Killer whale is from 1854 (earlier simply killer 1725); killer instinct is attested from 1931, originally in boxing.