An Etymological Dictionary of the German Language/Annotated/Bastard
Bastard, masculine, ‘bastard,’ from French bâtard, bastard (Italian bastardo), borrowed in the Middle Ages (Middle High German bastart). Middle English bast, ‘illegal marriage,’ and Old French fils de bast, ‘illegitimate son,’ indicate the primary meaning of the Romance word, which came to England with William I., and at a later period made its way to Scandinavia. The Old French bastard (French bâtard) has a Teutonic termination; see Bankert. The first part of the word, which in Middle English and Old French signifies ‘illegal marriage,’ is generally derived from Middle Latin and Romance bastum, ‘pack-saddle’; compare Italian and Spanish basto, French bât, ‘pack-saddle.’ Bastard would then mean ‘the son of a pack saddle’ (compare Bast) the saddles serving the Spanish muleteers as beds; compare Bankert. Scandinavian bastarðr, whence some would derive the modern European word, did not reach the North before 1200 A.D. nearly.