Amon Amarth was a rarely used name for Orodruin, the flaming mountain in northern Mordor where Sauron forged the One Ring.
The name was given because the volcano was linked in ancient and little-understood prophecies with the final end of the Third Age, when the One Ring was found again
Sindarin amon "hill" + amarth "fate, doom"
- ↑ J.R.R. Tolkien, "Nomenclature of The Lord of the Rings" in Wayne G. Hammond and Christina Scull (eds), The Lord of the Rings: A Reader's Companion