garde des reins

garde de rein: armor protecting the loins, hanging from the backpiece of the cuirass

“1786, To the back-piece of the cuirass for the protection of the loins, was hooked on a piece of armour, called Garde des Reins, or culettes; and the breast-piece was occasionally strengthened by an additional plate called a Plaquet.” — Francis Grose, A Treatise on Ancient Armour and Weapons, page 21.