The land beneath us. The realm of the dead. The realm of the evil dead
. You get the picture. Some parts are good, some parts are bad--depends on who you believe. The Greeks had two divisions; the Buddhists have eight. Christians think only evil people go there; the Celts said only gods go there. Go figure.
Names for the Underworld:
Sheol: Hebrew "the grave" Whether the Jews ever believed this was an actual place is up to debate; most Jews I've spoken to do not believe in an afterlife.
Gehenna: Hebrew; "valley of the sons of Hinnom". The dump outside Jerusalem's walls where they burned trash; also associated with the immolation of children in worship of Moloch. More of a New Testament type of thing.
Jahannam: Arabic, derived from Gehenna
Abyss: Book of Revelations' name.
The Lake of Fire: same.
- Hell/Hel: Anglo-Saxon, goddess of the underworld, daughter of Loki. "Concealed place," where dwells the serpent chewing on the roots of Yggdrasil.
- Muspelhiem: Norse, land of fire to the south. Sometimes identified with Hel/Hell.
- Niflheim: Norse, land of ice to the north, and realm of the dead.
- Valhalla: Norse; home of Odin and of the warriors who died in battle, where they feast and fight for eternity. Everyone else goes to Hell.
- Hades: Greek; god of underworld who gave his name to the place. "Half-blind"? divided into two areas:
"the firey place," an idea derived from the Hebrew Gehenna. Actually, it's derived from Proto-Indo-European *ṇdher- meaning "below, underground"
Uffern: Welsh, derived from the Latin "inferno"
Annwn/Annwfn: Welsh "the Not-world"? More an Otherworld of the sidhe than a land of the damned, or even the dead, but later conflated with Uffern.
Avalon: Welsh afallach--"Land of Apples." Where King Arthur and the Grail rest, a place of peace.
Tir na nOg: Irish "The Land of Youth"--where the blessed few get to go, instead of being reincarnated. Kinda like Nirvana. This concept is less hell than heaven, but still an underworld--an under-the-waves-world, actually.
Sidhe: The hollow hills, where the Tuatha De Danann dwell underground in Irish mythology.
Tech Duinn: The House of Donn, lord of the Dead in Irish myth.
The Blessed Isles: Celtic concept, similar as the above.
Buddhist hell: recounted under "hell," and I will not repeat it here.