late 13c., from O.Fr. robe "long, loose outer garment," originally "plunder, booty," from a Gmc. source (cf. O.H.G. rouba "vestments," presumably those taken from the enemy as spoils), from W.Gmc. *rauba, the stem that also yielded rob (v.). The verb is recorded from late 14c. Metonymic sense of "the legal profession" is attested from 1640s.