We recently discovered that “Gehenna” was actually a place in Jerusalem. It is well known because there were made child sacrifices in that place.
We also read that probably was an area where the outcasts and infected were dumped or maybe just where the garbage were burnt.
Anyway our first idea was related to the Jewish and Christian analogy of a lake of fire (or Hades/Hell) a place of punishment called “Gehenna”.
It is curious that the word Hell wasn’t in the Bible until the King James version (XVII century), Gehenna was the original word used.
Like we said before, probably was an analogy to a horrifying and stinky place.
This design shows the souls of the condemned struggling to reach the light, theirs bodies are snake-like as we see described in some parts of Divine Comedy. They are cursed to crawl for all eternity and that was their punishment.