In Norse mythology, the underworld (sometimes called Niflheim) and the goddess who ruled there. Hel, the goddess, was the youngest child of Loki and the giantess Angrboda. She's particularly nasty - her top half is that of a normal woman but her pelvis on down is corpse-style, rotting flesh.
Her hall in 'Helheim' is called Eljudnir - the home of the dead.
In early Germanic mythology, Hel was the goddess who ruled land of the dead. Later, particularly after the advent of Christianity, Hel became a place of punishment, similar to the Christian Hell.