kiss ass

Old English cyssan "to kiss," from Proto-Germanic *kussijanan (cf. Old Saxon kussian, Old Norse kyssa, Old Frisian kessa, Middle Dutch cussen, Dutch, Old High German kussen, German küssen, Norwegian and Danish kysse, Swedish kyssa), from *kuss-, probably ultimately imitative of the sound. Related: Kissed; kissing. For vowel evolution, see bury. There appears to be no common Indo-European root word for "kiss," though suggestions of a common ku- sound may be found in the Germanic root and Greek kynein "to kiss," Hittite kuwash-anzi "they kiss," Sanskrit cumbati "he kisses."

Some languages make a distinction between the kiss of affection and that of erotic love (cf. Latin saviari "erotic kiss," vs. osculum, literally "little mouth"). French embrasser "kiss," but literally "embrace," came about in 17c. when the older word baiser (from Latin basiare) acquired an obscene connotation. Insulting invitation kiss my ass is at least from 1705, but probably much older (cf. "The Miller's Tale").