Ethir Anduin
From Tolkien Gateway
The Ethir Anduin is the delta of the river Anduin, south of Pelargir. It is populated mostly by fishermen, and not very well defended. They sent some 100 fishermen spared from the boats for the defense of Minas Tirith.
Etymology
The Ethir Anduin is also known as the "Mouths of Anduin". Ethir is a Sindarin word meaning "Mouth" or, literally, "Out-flow". Anduin simply means "Long river".
Portrayal in adaptations
In Rankin/Bass' The Return of the King, Gandalf mentions the Ethir (wrongly pronounced Ee-thur) as he explains the coming of the Black ships to the audience.