topon. Mountains of Shadow, (lit.) Shadowy Mountains
Mountains in northern Beleriand translated “Mountains of Shadow” (S/106), but more accurately “Shadowy Mountains” (S/118, PE17/43). This name is a combination of the plural of orod “mountain” and the lenited plural of the adjective gwathren “shadowy, dim” (SA/gwath, VT42/9).
Conceptual Development: In Silmarillion drafts from the early 1930s, these mountains were first called Eryd-Lómin “Mountains of Shadow” (SM/139), a remnant of earlier G. lómin “shadowy”. This name was revised to N. Eredwethion “Shadowy Mountains” later in the 1930s (SM/268, LR/250), and similar forms S. Eryd-wethion and Eryd-wethian(d) appeared in notes from the 1950s as well (PE17/42-3, WJ/113). Generally, though, the name was changed to Ered Wethrin in Silmarillion revisions from the 1950s-60s, often appearing with the proper Sindarin plural of orod: S. Eryd (MR/297, WJ/113).