The easternmost of the successor-realms of Arnor after it was divided into three kingdoms (LotR/1039). As indicated on map to The Lord of the Rings, this region was later called the “Trollshaws”, but this does not appear to be the translation of the Sindarin name.

Possible Etymology: The second element is most like the lenited form -daur of taur “forest”. In Definitive Linguistic Notes (DLN) from 1959, Tolkien indicated that the initial element was the prefix rhu- “evil” (PE17/115), that is “*Evil Forest”. It seems very unlikely that the Dúnedain would have chosen this name for their kingdom, so this may be a later re-interpretation after that land fell to evil. Prior to the publication of PE17, several authors suggested the name might mean “*East Forest”, with the initial element being a prefixal form of rhûn “east” (e.g. Hammond and Scull, RC/690, or David Salo, GS/390).