Thalos
From Tolkien Gateway
Thalos was the second of the six rivers that rushed down from the Blue Mountains to meet the great River Gelion. The Thalos, whose name comes from the Elvish for "torrent", is important in the history of Men. It was in the high valley of its upper course that Bëor and his followers, the first Men to cross into Beleriand, made their camp, and where they were discovered by Elf King Finrod Felagund.