1. An orthopedic appliance that holds or supports part of the body; such as the arm.
2. Etymology: from about 1313, "armor for the arms"; from Old French brace, "arms", also "length measured by two arms"; from Latin bracchia, plural of brachium, "an arm"; from Greek brakhion, "arm, upper arm"; from brakhys, "short", in contrast to the longer forearm.

Applied to various devices for "fastening, tightening", with the notion of clasping the arms. The verb "to render firm" or "to steady by tensing" is from around 1440.