A forested region within Doriath (S/121). The name resembles Eregion, and probably has a similar meaning. Christopher Tolkien indicated its initial element is a variant form of ereg “holly” (SA/ereg), and its final element may be -ion² “-region” (as suggested by David Salo, GS/389).

Conceptual Development: In Silmarillion drafts from the 1930s, this region was first named Ilk. Region (LR/126), which was designated a Doriathrin [Ilkorin] name in The Etymologies, the genitive plural of Ilk. reg (Ety/ÉREK).