Source of the river Narog (S/209) translated “Ivrin’s Well” (WJ/139), a combination of eithel “spring, well” and the name Ivrin (SA/eithel).
Conceptual Development: In Silmarillion drafts from the 1930s, this name first appeared as N. Ivrineithil with the same elements and meaning (SM/313, LR/139). However, in this earlier form, the second element eithil seems to be plural. Silmarillion drafts of from the 1950s likewise had plural eithil: Eithil Ivrin (WJ/85, 139). Christopher Tolkien chose to use singular Eithel in The Silmarillion as published (S/209).
Location with a lake and falls (S/129, 139), the meaning of this name is unclear.
Conceptual Development: The name ᴱN. Ivrin first appeared in the Lays of Beleriand from the 1920s (LB/60), and N. Ivrin also appeared in Silmarillion drafts from the 1930s (SM/29, LR/260), but there are no clear explanations of its name, or even of the location itself other than its associated lake and falls. In the Gnomish Lexicon from the 1910s, there is an adjective G. ivrin “fertile” (GL/52), but it seems unlikely that it is related. Didier Willis suggested it might mean “✱of crystal, crystalline” based on the description of the lake (HSD/ivrin).