1610s, "pertaining to play or sport," from Latin ludicrus, from ludicrum "a sport, game, toy, source of amusement, joke," from ludere "to play," which, with Latin ludus "a game, play," perhaps is from Etruscan, or perhaps from PIE root *leid- "to play." Sense of "ridiculous" is attested from 1782. Related: Ludicrously; ludicrousness.