1223, "illegitimate child", from Old French
, "child of a nobleman by a woman other than his wife", probably from fils de bast "packsaddle son", meaning a child conceived on an improvised bed (saddles often doubled as beds while traveling), with pejorative ending -art. Alternate possibly is that the word is from Proto Germanic
*banstiz "barn", equally suggestive of low origin. Not always regarded as a stigma; the Conqueror is referred to in state documents as "William the Bastard." Figurative sense is from 1552; use as a vulgar term of abuse for a man is attested from 1830. Bastardize "debase" is from 1587.