1290, from O.Fr.
braon "fleshy or muscular part, buttock," from Frank.
*brado "ham, roast," from P.Gmc.
*bræd- (cf. O.H.G.
brato "tender meat," Ger.
Braten "roast," O.N.
brað "raw meat," O.E.
bræd "flesh"), from PIE
*bhre- "burn, heat," from base
*bureue- "to boil, bubble, effervesce, burn" (see
brew). 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]. In Eng., specifically "boar's flesh."
Brawny "characterized by muscle" is from 1599.
[brawn] 
