Definitions for "Annwn"
the other world; land of fairies.
Pronounced something like Ann-noon , this is the Celtic other world, the underworld, or the land of the dead. It is a place of great power and contained a cauldron that King Arthur had to travel into Annwn to fetch.
Underworld of Celtic myth. Ruled by Annwn, and, briefly, Pwyll (who exchanged forms with Annwn for one year and one day). Adapted as Annuvin in Lloyd Alexander's Prydain Chronicles.