"one who or that which repairs or mends," late 14c., agent noun from mend (v.). Originally especially "one who corrects what is wrong, a moral guide."
Entries linking to mender
mend v.
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.