11th cent. From Latin bracchium 'id.' Borrowed from Ancient Greek βραχίων (brakhíon) 'id.' From βρᾰχῠ́ς (brakhús) "short," crafted in reference to the shortness of the upper arm relative to the forearm.
From Proto-Indo-European *mreǵh- "short," "brief."
As a surname Brazo and Brazos, first found during the Middle Ages, given to those of strength or valor.
Asturian brazu, Portuguese braço, Galician brazo, Catalan braç, French bras, Italian braccio, Dalmatian braz, Aromanian brats, Romanian braț, Sardinian baltzu
"short," "brief" (see breve