The long, slow and resonant language used by the Ents. It was the habit of the Ents to string together descriptive words into a long chain of sound, so that names in Old Entish told the story of an object or person. A full conversation between Ents could thus take a considerable time, but this fitted the unhurried lifestyle of the Shepherds of the Trees.

The use of the word 'Old' in 'Old Entish' would normally imply that it represented a more ancient form of the Ents' language. In fact, this does not seem to be the case: Treebeard makes it clear that 'Old Entish' is the living language of the Ents, not a prior form. The tongue of the Ents is more commonly simply called 'Entish', so 'Old Entish' seems to be simply a longer name for the same language. The prefix 'Old' therefore appears to refer to the huge span of time over which Old Entish had been used, rather than indicating a different dialect or historical form.