expi

From Latin expiāre (to atone for, purify, appease), from ex- (out) + piāre (to propitiate, from pius, pious). The idea is to cleanse guilt "out" through pious acts. Yields expiate (to make amends), expiation (the act of atonement), and inexpiable (so grave it cannot be atoned for). A root confined to formal and literary registers.