Merriam-Webster Collegiate Dictionary - penance

 I. noun  Etymology: Middle English, from Anglo-French, from Medieval Latin poenitentia penitence  Date: 14th century  1. an act of self-abasement, mortification, or devotion performed to show sorrow or repentance for sin  2. a sacramental rite that is practiced in Roman, Eastern, and some Anglican churches and that consists of private confession, absolution, and a ~ directed by the confessor  3. something (as a hardship or penalty) resembling an act of ~ (as in compensating for an offense)  II. transitive verb  (~d; penancing)  Date: circa 1600 to impose ~ on