Origin: 1910–15; < F brassière bodice worn as an undergarment to support the breasts (now obs. in this sense), MF bracieres camisole, OF: armor for the arms, equiv. to bras arm (see brace) + -ière, suffix added to body part nouns, the resultant deriv. denoting an article for that part < L -āria-ary
18c., "woman's underbodice," from Fr. brassière "child's chemise, shoulder strap" (17c.), from O.Fr. braciere "arm guard," from bras "an arm," from L. brachium (see brace). Modern use is a euphemistic borrowing first recorded 1909.