mid-14c., maintenaunce, "wrongful interference in others' lawsuits by a lord or his followers," from Old French maintenance "upkeep; shelter, protection," from maintenir "to keep, sustain; persevere in" (see maintain). Meaning "action of upholding or keeping in good order" is from early 15c. That of "action of providing a person with the necessities of life," also "financial provision or support, that which maintains or supports" is from late 14c.
c. 1400, repaire, "maintenance, restoration;" 1590s, "act of restoring, restoration to a sound or good state after decay," from repair (v.1). Meaning "state or condition in respect to reparation" is from c. 1600, especially "good or sound condition kept up by repairing as needed." Repair-shop attested by 1877.
also peacekeeping, 1961 in the international sense, "regular maintenance by an organization of peace between nations or communities," from peace + keeping, verbal noun from keep (v.). Earlier "preservation of law and order" (mid-15c.), from verbal phrase keep the peace. Related: Peace-keeper (1570s).