1520s, "performance of more than duty requires," in Catholic theology, from Late Latin supererogationem (nominative supererogatio) "a payment in addition," noun of action from past participle stem of supererogare "pay or do additionally," from Latin super "above, over" (see super-) + erogare "pay out," from ex- "out" (see ex-) + rogare "ask, request" (see rogation).
