c. 1400, melioracioun, "improvement, act or process of making or becoming better," from Late Latin meliorationem (nominative melioratio) "a bettering, improvement," noun of action from past-participle stem of meliorare "to improve" (see meliorate). Meliorations in Scottish law were "improvements made by a tenant upon rented land."

1550s, "to make better, improve" (transitive), a back-formation from melioration or else from Late Latin melioratus, past participle of meliorare "improve," from Latin melior "better," used as comparative of bonus "good," but probably originally meaning "stronger," from PIE root *mel- (2) "strong, great." Intransitive sense of "to grow better, be improved" is from 1650s. Related: Meliorated; meliorating; meliorative.

Proto-Indo-European root meaning "strong, great." It forms all or part of: ameliorate; amelioration; meliorate; melioration; meliorism; multi-; multiform; multiple; multiply; multitude. It is the hypothetical source of/evidence for its existence is provided by: Greek mala "very, very much;" Latin multus "much, many," melior "better."