ereg (“holly tree”) + ion (#-ond commonly used suffix in the names of regions and countries) #The suffix could be reinterpreted or might have blended with Dor. -ion - plural genitive suffix, as in Dor. Region
Eregionnoun. land of holly trees
Eregionplace name. Hollin
eregionplace name. Hollin, Hollin, (lit.) Holly-region, Holly-region, Land of Holly
The realm of the Noldor in Middle Earth during the Second Age, translated “Hollin” (LotR/305) but more accurately “Holly-region” (RC/772). This name is a combination of ereg “holly” and the suffix -ion² “-region” (SA/ereg; PE17/37, 42).
Conceptual Development: In Lord of the Rings drafts from the 1940s, this region was first named N. Nan-eregdos in a chronology for Chapter XV (TI/166), but appeared in the draft text as N. Eregion (TI/124-5). This form also appeared in the Etymologies, already with the derivation given above (Ety/ÉREK).