late 14c., "to help, support, maintain," also "fill up, make up for," from Old French soupplier "fill up, make full" (Modern French suppléer) and directly from Latin supplere "fill up, make full, complete," from assimilated form of sub "up from below" (see sub-) + plere "to fill" (from PIE root *pele- (1) "to fill"). The meaning "furnish, provide" first recorded 1520s. Related: Supplied; supplying.
early 15c., "assistance, relief, act of supplying," from supply (v.). Meaning "that which is provided, quantity or amount of something provided" is attested from c. 1600. Meaning "person who temporarily takes the place of another" (especially a minister or preacher) is from 1580s. In the political economy sense (corollary of demand (n.)) it dates from 1776; supply-side (adj.) in reference to economic policy is attested from 1976; as a noun by 1922. Supplies "necessary provisions held for distribution and use" is from c. 1650.