accumulate (v.) Look up accumulate at Dictionary.com
1520s, "to heap up" (transitive), from Latin accumulatus, past participle of accumulare "to heap up, amass," from ad- "in addition" (see ad-) + cumulare "heap up," from cumulus "heap" (see cumulus). From 1759 in intransitive sense of "grow in size or number." Related: Accumulated; accumulating.