boisterous (adj.) Look up boisterous at
late 15c., unexplained alteration of Middle English boistous (c. 1300) "rough, coarse (as of food), clumsy, violent," which is of unknown origin, perhaps from Anglo-French bustous "rough (road)," which is perhaps from Old French boisteos "curved, lame; uneven, rough" (Modern French boiteux), itself of obscure origin. Another guess traces it via Celtic to Latin bestia. Used of persons from 1560s. Related: Boisterously; boisterousness.