c. 1200, "to repair" (clothes, a tool, a building), "remove defects" (from something broken, defaced, deranged, or worn), from a shortened form of Old French amender "correct, set right, make better, improve" (see amend). Meaning "to put right, atone for (faults and errors), amend (one's life), repent" is from c. 1300. Intransitive sense of "to grow better, improve" is from late 14c. Related: Mended; mending.