One of the seven streams from which Ossiriand got its name (S/123). The stream divided around the island Tol Galen, and was thus named “Double Stream” (SI/Adurant), a compound of adu “double” and rant “course” (SA/rant). Given the river’s location in Ossiriand, this name might be Nandorin instead.
Conceptual Development: In The Etymologies from the 1930s, the name Adurant was designated Ilkorin, but otherwise had the same meaning (Ety/AT(AT)). Like many of the river names in Ossiriand, Tolkien did not give a new etymology of the name after he abandoned the Ilkorin language.
adu (Ilk (AS?) “double”) + rant (“load, vein”)