early 15c., "of or belonging to animals," from Middle French brut "coarse, brutal, raw, crude," from Latin brutus "heavy, dull, stupid," an Oscan word, from PIE root *gwere- (2) "heavy" (see grave, adj.). Before reaching English the meaning expanded to "of the lower animals." Used of human beings from 1530s.

1610s, from brute, adj..