What fictional race did J.R.R. Tolkien invent the word “Ent” to describe?

J.R.R. Tolkien used the word “Ent” for the tree shepherds of Middle-earth.

Ents are ancient, tree-like beings who protect and care for forests. Their name comes from an Old English word meaning giant, and Tolkien’s Ents also connect with older traditions about speaking or supernatural trees. In The Lord of the Rings, the best-known Ent is Treebeard, who guides Merry and Pippin through Fangorn Forest.

The Ents play a decisive role when they attack Isengard after learning how Saruman’s forces have damaged Fangorn and its trees. Their march shows that the natural world can act collectively against industrial destruction.

Ents are not simply ordinary trees that have come alive, nor are they the same as Huorns, a related but more mysterious tree-like category. “Tree shepherds” is Tolkien’s own descriptive phrase for their role.