Know how to use "fewer" and "less"? Find out.
early 15c., "action of gathering together," from Middle French congestion (14c.), from Latin congestionem (nominative congestio), noun of action from past participle stem of 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)
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.
When the offered load of a data communication path exceeds the capacity.