embolus (n.)

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" from assimilated form of en "in" (see en- (2)) + ballein "to throw" (from PIE root *gwele- "to throw, reach"). Medical sense in reference to obstruction of a blood vessel is from 1866. Related: Embolic.