One of the seven streams from which Ossiriand got its name (S/123), and is simply thalos “torrent” used as a name (Ety/STAL). Given the river’s location in Ossiriand, this name might be Nandorin instead.

Conceptual Development: In The Etymologies from the 1930s, the name Thalos was designated Ilkorin, with the derivation given above (Ety/STAL). Like many of the river names in Ossiriand, Tolkien did not give a new etymology of the name after he abandoned the Ilkorin language.