Fangorn is the name of an old forest in Tolkien's The Lord of the Rings and also the name of the eldest Ent who lives in that forest, the last forest that ents (male ents, anyhow) are known to exist in. Fangorn means simply "treebeard" in the common tongue, the Pippin and Merry call him this when they befriend him after escaping the orcs who have kidnapped them. Treebeard is a slow fellow to whom haste is anathema, but when roused (like by people cutting down his trees!) he gets downright kick-ass, to which Saruman can attest.