Is it ensure, insure, or assure?
mid-15c., from Late Latin implementem "a filling up" (as with provisions), from Latin implere "to fill," from assimilated form of in- "into, in, on, upon" (see in- (2)) + plere "to fill" (see pleio-). Sense of "tool" is 1530s, from notion of things provided to do work, that which "fills up" or "completes" a household (c.1500).
1806, originally chiefly in Scottish, where the noun was a legal term meaning "fulfillment," from implement (n.). It led to the wretched formation implementation, first recorded 1913. Related: Implemented.