A tributary of Gelion, later named Rathlóriel (S/123), translated “rushing, impetious” by Christopher Tolkien (SI/Ascar). It is simply the adjective (N.) ascar “rushing” used as a name. Given the river’s location in Ossiriand, this name might be Nandorin instead.
Conceptual Development: This name appeared in Silmarillion drafts from the 1930s (SM/135, SM/325) along with the variant Asgar (SM/325, WJ/336). In The Etymologies, it was designated an Ilkorin name, Ilk. Ascar, though the adjective ascar was designated both Noldorin and Ilkorin, along with a Noldorin-only variant asgar (Ety/SKAR). Like many of the river names in Ossiriand, Tolkien did not give a new etymology of the name after he abandoned the Ilkorin language. Since [sk] usually became [sg] in Sindarin, this name is likely either archaic or dialectal.