The mountains south of Dorthonion where Ungoliant once dwelled (S/95, 121). This name is a combination of the plural of orod “mountain” and the name Gorgoroth, which was also used for a region in Mordor (LotR/636).
Conceptual Development: In Silmarillion drafts from the 1930s, this name appeared as N. Ered Orgoroth (LR/298), because names and nouns in this position underwent soft mutation in Noldorin, as opposed to later Sindarin where only adjectives were lenited in this position. The name was changed in Silmarillion revisions from the 1950s-60s, first to Ered Gorgorath with an a (MR/127, WJ/129), then Ered Gorgoroth (MR/297). In later writings this name occasionally appeared with the proper Sindarin plural of orod: S. Eryd (MR/297, WJ/319).
ered (pl. of orod “mountain”), gor (“extreme horror” duplicated first syllable of goroth) + (n-)goroth (“horror”)