The mountains in eastern Beleriand and western Eriador named after the region Lindon (S/123). This name is a combination of the plural of orod “mountain” with that region name.
Conceptual Development: In Silmarillion drafts from the 1930s, this name first appeared as N. Eredlindon, but it was first translated “Blue Mountains” (LR/126, LR/260). The second element of this name was originally derived from N. glinn “(pale) blue”, but in The Etymologies Tolkien rejected this word (Ety/GLINDI, EtyAC/GLINDI). He then revised this name’s derivation to the one given above, though at this stage, Lindon was an Ilkorin name (Ety/LIN², ÓROT). Despite this change, Tolkien still referred to them as the “Blue Mountains” in The Lord of the Rings (LotR/43), but with a new Sindarin name Ered Luin.
Land of the Nandor in eastern Beleriand, translated “Land of Music” (S/123), based on lind “song”. This name was originally Nandorin, adopted into Sindarin (WJ/385), because normally [[s|[nd] became [nn]]] in Sindarin.
Conceptual Development: In Silmarillion drafts from the 1930s, the name Ilk. Lindon was translated “Region of Music” and provided a new explanation for the name of the mountain range Eredlindon (LR/267). In The Etymologies, it was translated “Musical Land” and designated Ilkorin, appearing beside a variant Lhinnon which is probably the Noldorin form of the name (Ety/LIN²).