Thrihyrne refers to the northernmost three steep-sided peaks of the White Mountains, which also marked the southern edge of the wide Gap of Rohan.
They stood out above the gorge of Helm's Deep, which wound into them, and could be seen behind the Hornburg, built on an outlying northern spur known as the Hornrock.
The name 'Thrihyrne' is Old English, and means simply 'three horns'.
- ↑ J.R.R. Tolkien, The Lord of the Rings, The Two Towers, "Helm's Deep"