The northernmost and longest lasting of the successor-realms of Arnor after it was divided into three kingdoms (LotR/1039). Tolkien did not translate the name, but as suggested by Hammond and Scull, it might mean “Realm of the Edain” (RC/690). If so, its initial element may be a form of arthor “realm” also seen in the ancient name of Arnor, Arthor na Forlonnas “Realm of the North-harbourage” (PE17/28). The second element is almost certainly the plural Edain “(High) Men” of the noun Adan.