Why is the place that that wicked are punished for their sins after death termed Gehinnom? Is there is an association with Gei ben Hinnom where idolatry was performed? If so why was this place singled out?
Why is it called "Gehinom" (lit. valley of screams)? Because the screams "hinom" roar out from one end of the world to the other. - meseches Gehinom quoted from Reishis Chachma - Shaar Yira Ch.13
found here http://dafyomireview.com/gehinom.php footnote 1
Chizyonos HaRama connects it to Gei ben Hinnom that those who receive it after death are themselves responsible for this punishment.