Fangorn Forest was named after Treebeard who was also known as Fangorn. It was on the Eastern side of the Misty Mountains and was part of a larger forest of trees across western Middle Earth. Over the ages, the trees diminished, and the Ents confined themselves to one of the few remaining parts of the woods, Fangorn. Although, Merry and Pippin were able to persuade them to go and attack Saruman and lay siege to Isengard.