What's the difference between gehenna and gehenom?
Gehenna
Definition:
(n.) The valley of Hinnom, near Jerusalem, where some of the Israelites sacrificed their children to Moloch, which, on this account, was afterward regarded as a place of abomination, and made a receptacle for all the refuse of the city, perpetual fires being kept up in order to prevent pestilential effluvia. In the New Testament the name is transferred, by an easy metaphor, to Hell.