Annwn

Annwn or Annwfn or Annwvyn (Middle Welsh, Annwvn, Annwyn, Annwyfn or Annwfyn) was the Otherworld in Welsh mythology. Ruled by Arawn, or much later by Gwyn ap Nudd, it was essentially a world of delights and eternal youth where disease is absent and food is ever-abundant. It later became Christianised and identified with the land of souls that had departed this world. In modern Breton, "Anaon" is synonymous with paradise rather than hell and the phrase "mont da Anaon", literally "to go to Anaon", is a euphemism for "to die".

Read more about Annwn:  Name and Etymology, Mythical Locations, Appearances in Welsh Literature, Annwn in Modern Culture