gardbrace
A piece of armor which augments the pauldron in protecting the shoulder.
Some plates were bent up at the edges, or “turned.” Turns were made at the top of the breastplate and around the armholes. The top edges of the pauldrons were turned until the gardbraces were added. Then the turn was added to them.
1963, Sean Morrison, Armor, Ty Crowell Company
Where it comes from
Apparently a variant of gardebras. for the semantic development, compare passguard.
Adapted from the Wiktionary entry gardbrace (CC BY-SA 4.0).