also kill-joy, 1776, from kill (v.) + joy. Kill formerly was used with other stems (for example kill-courtesy "boorish person," kill-cow "bully, big man," etc.; also compare Kellogg).
Entries linking to killjoy
kill v.
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").
joy n.
c. 1200, "feeling of pleasure and delight;" c. 1300, "source of pleasure or happiness," from Old French joie "pleasure, delight, erotic pleasure, bliss, joyfulness" (11c.), from Latin gaudia "expressions of pleasure; sensual delight," plural of gaudium "joy, inward joy, gladness, delight; source of pleasure or delight," from gaudere "rejoice," from PIE root *gau- "to rejoice" (cognates: Greek gaio "I rejoice," Middle Irish guaire "noble").
As a term of endearment from 1580s. Joy-riding is American English, 1908; joy-ride (n.) is from 1909.