Annwfn is a Welsh word with roots in Welsh mythology. It refers to the otherworld or the underworld, which is home to gods and goddesses in Celtic mythology. There are several synonyms for Annwfn, depending on the context and the interpretation of the word. The concept of Annwfn is similar to that of Hades in Greek mythology, the land of the dead. Other possible synonyms for Annwfn include Tir na nOg, Avalon, and Mag Mell, all of which are mythical otherworlds described in Celtic folklore. The concept of Annwfn continues to inspire art, literature, and music to this day and remains an important part of Welsh culture.