late 14c., from Late Latin propitiationem (nominative propitiatio) "an atonement," noun of action from past participle stem of Latin propitiare "appease, propitiate," from propitius "favorable, gracious, kind, well-disposed," from pro- "forward" (see pro-) + stem related to petere "to make for, go to; seek, strive after; ask for, beg, beseech, request" (see petition, n.).The sense in Latin is perhaps because the word originally was religious, literally "a falling or rushing toward," hence "eager," and, of the gods, "well-disposed." Earliest recorded form of the word in English is propitiatorium "the mercy seat, place of atonement" (c.1200), translating Greek hilasterion.