Merriam-Webster's Collegiate® Dictionary, 11th Edition
PENITENTIARY
I. noun (plural -ries)
Etymology: Middle English penitenciary, from Medieval Latin poenitentiarius, from poenitentia
Date: 15th century
1. an officer in some Roman Catholic dioceses vested with power from the bishop to deal with cases of a nature normally handled only by the bishop, a cardinal presiding over a tribunal of the Roman curia concerned with dispensations and indulgences, a public institution in which offenders against the law are confined for detention or punishment,
II. adjective
Date: 1577
penitential , of, relating to, or incurring confinement in a penitentiary