" Originally Ge bene Hinnom, that is (' valley of the sons of Hinnom'), a deep, narrow glen to the south of Jerusalem where the "idolatrous Jews offered their children in sacrifice to Molech(2Chr28:3. 33:6. Jer7:31. 19:2-6). This valley afterwards became the common receptacle for all the refuse of the city. There the dead bodies of animals & of criminals & all kinds of filth were cast & consumed by the "fire kept always burning". It thus in the process of time became the image of the place of everlasting destruction.In this sense it is used by our Lord Matt5:22,29,30.10:28. 18:9. 23:15,33.Luke 12:5.James 3:6"
www.kingjamesbibleonline.org/Gehenna.php4
NB: These verses in Matthew, Luke & James has often been mistranslated as "hellfire" or "hell". Please, Shine your eyes, Gehenna is not hellfire , & not a place of torment. Anything thrown in there was burnt to ashes. Gehenna is a fitting symbol of destruction (for the dead without any prospect of resurrection for them)