gardebras
A piece of armor which protects the arm.
The gardebras here probably implies the whole armour for the arms, consisting of pauldrons, brassarts, elbow-pieces, and vambraces, though there is a gardebras of the more antient kind so formed as to screw on the bridle-arm […]
Where it comes from
Either borrowed from (Middle) French garde-bras, gardebras, or modified (under the influence of that word) from Middle English garbrasse, itself from that (Middle) French word.
Adapted from the Wiktionary entry gardebras (CC BY-SA 4.0).