From Tolkien Gateway

Brithon was a river of Beleriand that had its wells in the hills lying north-west in West Beleriand south of the Ered Wethrin. It ran south through the Falas to the bay of Brithombar where it met the sea Belegaer.

Etymology[edit | edit source]

Brithon is Ilkorin for "pebbly".[1]