https://books.openedition.org/pcjb/5944Here's a text in French. A small summary.
Use of leather as protection :
illustration 1, apron under the shield.
illustration 2, protection in contact with game.
Raw or tanned skins serv as clothing for the poor.
They are also used to camouflage themselves.
A text from the 2nd century BC says that the pouch of the slings are made with leather. The text is ambiguous about the material of the straps : leather or vegetable ?