early 14c., from Old French prologue (12c.) and directly from Latin prologus, from Greek prologos "preface to a play, speaker of a prologue," literally "a speech beforehand," from pro "before" (see pro-) + logos "discourse, speech," from legein "to speak," from PIE root *leg- (1) "to collect, gather," with derivatives meaning "to speak (to 'pick out words')."
