1520s, "to heap up" (transitive), from Latin accumulatus, past participle of accumulare "to heap up, amass," from ad "to," here perhaps emphatic (see ad-), + cumulare "heap up," from cumulus "heap" (from suffixed form of PIE root *keue- "to swell"). From 1759 in intransitive sense of "grow in size or number." Related: Accumulated; accumulating.
late 15c., "that which is heaped up, an accumulated mass," from Latin accumulationem (nominative accumulatio) "a heaping up," noun of action from past-participle stem of accumulare "to heap up, amass," from ad "to," here perhaps emphatic (see ad-), + cumulare "heap up," from cumulus "heap" (from suffixed form of PIE root *keue- "to swell"). Meaning "act of heaping up" is from c. 1600.
formerly also accrew, mid-15c., acreuen, in reference to property, etc., "to fall to someone as an addition or increment," from Old French acreue "growth, increase, what has grown," fem. of acreu, past participle of acreistre (Modern French accroître) "to increase," from Latin accrescere "grow progressively, increase, become greater," from ad "to" (see ad-) + crescere "grow" (from PIE root *ker- (2) "to grow"). Related: Accrued; accruing. Apparently an English verb from a French noun because there is no English noun to go with it until much later (the earliest seems to be now-obsolete accrue, 1570s), unless the record is defective. From late 15c. as "happen or result as a natural growth;" from 1881 as "gain by increment, accumulate." Alternative verb accrete "grow by adhesion" (1784) is rare, as is accresce (1630s), from Latin accrescere.
1610s, "act of growing by organic enlargement;" 1650s as "that which is formed by continued growth from without," from Latin accretionem (nominative accretio) "an increasing, a growing larger" (as of the waxing moon), noun of action from past-participle stem of accrescere "grow progressively, increase, become greater," from ad "to" (see ad-) + crescere "grow" (from PIE root *ker- (2) "to grow"). It goes with the verb accrue. Related: Accretional; accretionary.
1610s, "vouch for, bring into credit," from French accréditer, earlier acrediter, from à "to" (see ad-) + créditer "to credit" (someone with a sum), from crédit "credit" (see credit (n.)). Falsely Latinized in French. The word was rare in English in the original sense but became common in the meaning "confer credit or authority on" (1794). Related: Accredited; accrediting.