Prop (?), n. A shell, used as a die. See Props.
[1913 Webster]

Prop, n. [Akin to LG., D., & Dan. prop stopple, stopper, cork, Sw. propp, G. pfropf. See Prop, v.] That which sustains an incumbent weight; that on which anything rests or leans for support; a support; a stay; as, a prop for a building. “Two props of virtue.” Shak.
[1913 Webster]