1590s, "action of gathering together," from Fr. congestion (16c.), from L. congestionem, noun of action from congerere (see congest). Medical sense is from 1630s; meaning "a crowding together of people, traffic, etc." is from 1883.
congestion con·ges·tion (kən-jěs'chən) n. The presence of an abnormal amount of fluid in a vessel or organ; especially excessive accumulation of blood, due either to increased afflux or to obstruction of return flow.