The language spoken by the Ents in J.R.R. Tolkien’s The Lord of the Rings is called Entish.
Entish is the language of the tree-shepherds of Middle-earth. Tolkien describes it as extremely slow, deliberate and difficult for other peoples to learn. Its structure reflects the Ents’ patient way of thinking: an Entish discussion may take a very long time because the speakers consider the history and nature of things before reaching a conclusion.
The Ents’ language is also described as unique to them. Treebeard explains that the Ents did not simply borrow a language from another people, although they were interested in the speech of Elves and learned from them. In the narrative, Treebeard’s long account to Merry and Pippin demonstrates the language’s measured style.
Westron is the Common Speech, Black Speech is associated with Mordor, and Adûnaic was a language of Númenor. None of those names refers to the Ents’ own tongue.