Middle English roren, "shout out, cry out with a full, loud, continued sound," from Old English rarian "roar, wail, lament, bellow, cry," probably of imitative origin (compare Middle Dutch reeren, German röhren "to roar;" Sanskrit ragati "barks;" Lithuanian rieju, rieti "to scold;" Old Church Slavonic revo "I roar;" Latin raucus "hoarse," all alike probably imitative).
Of animals, the wind, etc., early 14c. Sense of "laugh loudly and continuously" is by 1815. The meaning "travel in a motor vehicle making a loud noise" is by 1923. Related: Roared; roaring.
late 14c., rore, "the loud, continued cry of a large beast," from roar (v.) and Old English gerar. Of other full, loud, continued, confused sounds by c. 1400; specifically of thunder and cannon by 1540s.