An uncomfortable garment worn as a form of penance. Made from goat or horse hair, it came in two varieties; said shirt or a loin girdle. The penitent would wear one underneath his or her clothes and continue normal every-day life. As normal as one could handle, anyway.

Lancelot was thought to have worn one under his armour to try and get over Guinevere. I guess the itching and scratching was all for nothing.