From Middle English rok, roke, from Old English hrōc, from Proto-West Germanic *hrōk, from Proto-Germanic *hrōkaz (compare Old Norse hrókr, Saterland Frisian Rouk, Dutch roek, obsolete German Ruch), from Proto-Indo-European *kerk- (compare Old Irish cerc ("hen"), Old Prussian kerko ("loon, diver"), dialectal Bulgarian кро́кон ("raven"), Ancient Greek κόραξ ("crow"), Old Armenian ագռաւ, Avestan 𐬐𐬀𐬵𐬭𐬐𐬀𐬙𐬀𐬝, Sanskrit कृकर), Ukrainian крук ("raven").
From Middle English rook, roke, rok, from Old French roc, ultimately from Persian رخ, from Middle Persian lhw' ("rook, castle (chess)"), possibly from Sanskrit रथ ("chariot"). Compare roc.