Gehenna translates as the Valley of Hinnom, now a very green and fertile land but 2000 years ago indeed the dumpster fire of Jerusalem. The bodies of criminals were burned there and didn't get a proper burial, so they weren't lying when they said to kids 'if you do bad things you will burn in the fires of Gehenna'!

Our contemporary image of hell is indeed more of a cultural creation by the likes of Dante and Milton.

The word Hell is actually derived from norse mythology. Hel was the goddess of the Viking underworld.