Bastard
Middle English: via Old French from medieval Latin bastardus, probably from bastum ‘packsaddle’; compare with Old French fils de bast, ‘packsaddle son’ (i.e. the son of a mule driver who uses a packsaddle for a pillow and is gone by morning).
wiktionary
From Middle English bastard, bastarde, from Anglo-Norman bastard(“illegitimate child”), from Frankish *bāst(“marriage”) (probably via Medieval Latin bastardus; compare Middle Dutch bast(“lust, heat”)) and derogatory suffix -ard(pejorative agent noun suffix), from Proto-Germanic *banstuz(“bond, tie”) (compare West Frisian boask, boaste(“marriage”)), from Proto-Indo-European *bʰendʰ-(“to tie, bind”); or equivalent to bast + -ard. Cognate with French bâtard(“bastard”), West Frisian bastert(“bastard”), Dutch bastaard(“bastard”), German Bastard(“bastard”), Icelandic bastarður(“bastard”). Probably originally referred to a child from a polygynous marriage of heathen Germanic custom — a practice not sanctioned by the Christian churches. Related to boose.
Alternatively, the Old French form may originate from the term fils de bast(“ packsaddle son”), meaning a child conceived on an improvised bed (medieval saddles often doubled as beds while traveling).
etymonline
bastard (n.)
"illegitimate child," early 13c., from Old French bastard "acknowledged child of a nobleman by a woman other than his wife" (11c., Modern French bâtard), 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.
Compare German bänkling "bastard; child begotten on a bench" (and not in a marriage bed), the source of English bantling (1590s) "brat, small child." Bastard was 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 generic vulgar term of abuse for a man is attested from 1830. 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").
As an adjective from late 14c. It is used of things spurious or not genuine, having the appearance of being genuine, of abnormal or irregular shape or size, and of mongrels or mixed breeds.
