The term "hair shirt" is now used as a phrase to refer to some form of self-imposed penance or punishment. The term is derived from the Christian faith. As a word it is a noun that refers to a coarse type of haircloth garment that is worn around the skin causing discomfort as a form of penance or by religious ascetics. The use of the hair shirt can be traced back to the thirteenth century. A hair shirt is usually made of goat's skin and is thus coarse or rough against the skin. It was believed to cause enough discomfort to drive away the thought of sins of the flesh. Examples of its use as a phrase include "He went on wearing a hair shirt despite the fact that everyone knew the accident was not his fault".