Dark Mountains
From Tolkien Gateway
The Dark Mountains was the original name for the range of deeply forested hills that ran through the northern part of Greenwood the Great, whose name is a translation of the Elvish Emyn Duir. When the shadow of Dol Guldur fell on the forest, it was renamed 'Mirkwood', and this range of high hills came to be called the Mountains of Mirkwood.
