1660s, "stopper, wedge," from Latin embolus "piston of a pump," from Greek embolos "peg, stopper; anything pointed so as to be easily thrust in," also "a tongue (of land), beak (of a ship)," from emballein "to insert, throw in, invade" (see emblem). Medical sense in reference to obstruction of a blood vessel is from 1866. Related: Embolic.