"The earlier name for Cûm Arelaid was "Umb Dolen". According to the learned work of Lamhir the Wise, the word "umb", "vale", in this name was borrowed by early Númenórean explorers from the Daenael speech spoken of the Men of the White Mountains. "Umb" was only found in a few provincial place-names of very ancient lineage; in names of more recent origin, "umb" has been supplanted by "Cûm", a word from the modern Dunael tongue descended from the ancient ancestor Daenael. Lamhir also proposes that both "umb" and "Cûm" are distantly akin to Quenya "tumbo", "valley", and Sindarin tum,though we find the suggestion of any connection, however remote, between the noble Elven-tongues and the crude jargons of the mountain-folk to be distasteful" -Findegil
Cûm Arelaidh (Dn."Vale of Stone Burials") was a vale of the White Mountains just west of the Lefnui. This desolate and isolated valley served as a place of burial for the Daen Lintis of Hairaverkien, who had erected numerous standing stones to mark the sacred ground. However with the exception of a single barrow mound marking the grave of an eponymous acestor, the graves of the dead had taken the form of catacombs delved into the surrounding mountains. This was not a common practice among the Dunir of Andrast, and reflected the Coentis origins of Hairaverkien's clans. To the Dúnedain, the vale was known as Umb Dolen.
References
- MERP:Southern Gondor - The Land