brawn: [14] English acquired brawn from Anglo- Norman braun or Old French braon, which meant ‘flesh, muscle’, but the word’s ultimate origins are not so much a matter of physiological substance as of suitability for cooking and eating. For the source of the French word was Germanic *brādon ‘roast’, which can probably be traced back to Indo-European *bhrē- ‘burn, heat’ (ancestor also of English braise, breath, breed, and brood). Brawn was thus originally a ‘piece of meat suitable for roasting’. => braise, breath, breed, brood
brawn (n.)
late 13c., from Old French braon "fleshy or muscular part, buttock," from Frankish *brado "ham, roast" or some other Germanic source, from Proto-Germanic *bred-on- (cognates: Old High German brato "tender meat," German Braten "roast," Old Norse brae "raw meat," Old English br?d "flesh"), from PIE *bhre- "burn, heat," from root *bhreu?- "to boil, bubble, effervesce, burn" (see brew (v.)). The original sense is "piece of meat suitable for roasting." "The specific sense 'boar's flesh' is exclusively of English development, and characteristic of English habits" [OED].