Gehenna is one word used for Hell. It comes from the Hebrew Gey-Hinnom, literally "valley of Hinnom." This word originated as the name for a place south of the old city of Jerusalem where the city's rubbish was burned. At one time, live babies were thrown crying into the fire under the arms of the idol, Moloch, to die there. This place was so despised by the people after the righteous King Josiah abolished this hideous practice, that not only was it made into a garbage heap. Bodies of diseased animals and executed criminals were thrown there and burned.
In the Dungeons and Dragons fantasy role-playing game, Gehenna (in the current edition of the game, the Bleak Eternity of Gehenna; also, The Fourfold FurnacesCook, Monte: The Planewalker's Handbook, p. 21, TSR 2620 or The Fires of Perdition), is a plane of existence of neutral evil/lawful evil alignment. It is one of a number of alignment-based Outer Planes that form part of the standard Dungeons & Dragons (D&D) cosmology, used in the Planescape, Greyhawk and some editions of the Forgotten Realms campaign settings. It borders the Gray Waste of Hades and the Nine Hells of Baator.