A hair shirt or rough garment traditionally worn against the skin as a form of self-imposed suffering or religious penance.
From Late Latin cilicium, referring to a coarse fabric originally made in Cilicia (in modern-day Turkey). The term evolved to mean any rough penitential garment, not just the original Cilician cloth.
Medieval monks and saints would wear cilices under their regular clothes as a secret form of self-punishment, believing suffering brought them closer to God—some were so uncomfortable they left permanent scars, and yes, people still wear them today as acts of faith.
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