bastardyoudaoicibaDictYouDict[bastard 词源字典]
bastard: [13] The idea underlying the word bastard appears to be that of a child born of an impromptu sexual encounter on an improvised bed, for it seems to echo Old French fils de bast, literally ‘packsaddle son’, that is, one conceived on a packsaddle pillow. If this is the case, the word goes back to medieval Latin bastum ‘packsaddle’, whose ultimate source was Greek bastázein ‘carry’; this passed via Old French bast, later bat, into late Middle English as bat, which now survives only in batman [18].

The derived form is first found in medieval Latin as bastardus, and this reached English via Old French bastard. Its modern usage as a general term of abuse dates from the early 19th century.
=> batman[bastard etymology, bastard origin, 英语词源]
bastard (n.)youdaoicibaDictYouDict
"illegitimate child," early 13c., from Old French bastard (11c., Modern French bâtard), "acknowledged 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 (see -ard). Alternative 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 of "something not pure or genuine" is late 14c.; use as a vulgar term of abuse for a man is attested from 1830. As an adjective from late 14c. Among the "bastard" words in Halliwell-Phillipps' "Dictionary of Archaic and Provincial Words" are avetrol, chance-bairn, by-blow, harecoppe, horcop, and gimbo ("a bastard's bastard").