Cilice

A cilice /ˈsɪlᵻs/ was originally a garment or undergarment made of coarse cloth or animal hair (a hairshirt) worn close to the skin. It was used in some religious traditions to induce discomfort or pain as a sign of repentance and atonement.

Cilices were originally made from sackcloth or coarse animal hair so they would irritate the skin. Other features were added to make cilices more uncomfortable, such as thin wires or twigs.