late Old English curs "a prayer that evil or harm befall one," of uncertain origin, perhaps from Old French curuz "anger," or Latin cursus "course." Connection with cross is unlikely. No similar word exists in Germanic, Romance, or Celtic. Curses as a histrionic exclamation is from 1885. The curse "menstruation" is from 1930. Curse of Scotland, the 9 of diamonds in cards, is attested from 1791, but the origin is obscure.

Old English cursian, from the source of curse, n.. Meaning "to swear profanely" is from early 13c. Related: Cursed; cursing.