late 14c., "to help, support, maintain," also "fill up, make up for," from O.Fr. supplier "fill up, make full," from L. supplere "fill up, complete," from sub "up from below" + plere "to fill" (see plenary). The meaning "furnish, provide" first recorded c.1520.
1423, "assistance, relief," from supply (v.). Meaning "quantity or amount of something provided" is attested from 1607. In the political economy sense (corollary of demand) it dates from 1776. Supply-side in ref. to economic policy is attested from 1976. Supplies "provisions" is from c.1650.