§ Of the Return of the Noldor The Silmarillion

Then Angrod was wrathful and went forth from the council. Maedhros indeed rebuked Caranthir; but the greater part of the Noldor, of both followings, hearing his words were troubled in heart, fearing the fell spirit of the sons of Fëanor that it seemed would ever be like to burst forth in rash word or violence. But Maedhros restrained his brothers, and they departed from the council, and soon afterwards they left Mithrim and went eastward beyond Aros to the wide lands about the Hill of Himring. That region was named thereafter the March of Maedhros; for northwards there was little defence of hill or river against assault from Angband. There Maedhros and his brothers kept watch, gathering all such people as would come to them, and they had few dealings with their kinsfolk westward, save at need. It is said indeed that Maedhros himself devised this plan, to lessen the chances of strife, and because he was very willing that the chief peril of assault should fall upon himself; and he remained for his part in friendship with the houses of Fingolfin and Finarfin, and would come among them at times for common counsel. Yet he also was bound by the oath, though it slept now for a time.