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
bras·siere (brə-zîr') n. A woman's undergarment worn to support and give contour to the breasts.
[French brassière, child's jacket with sleeves, brassiere, from Old French braciere : bras, arm (from Latin brācchium; see brachium) + -iere, -ier, one associated with; see -er1.]
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.