Yes, my understanding is that "Gehenna" (however it's spelled) came from "Valley of Hinnom" south of Jerusalem.
Moral or spiritual cleansing is the Catholic understanding of what happens in the place (or rather, the state) of Purgatory --- a word that means, literally, purification.
Going through a washing machine sounds like a good description. It's the sort of suffering which is ultimately therapeutic, like the healing of a body of broken bones. The souls there are not in despair, they're hopeful.
When my boys were kids, I explained it was like having tar scoured off of you with a scrubbing pad. Not pleasant, but you know you'll the shiny and sparkly afterwards. :o)
Here’s the Chabad take on the broader topic:
https://www.chabad.org/library/article_cdo/aid/282508/jewish/What-Happens-After-We-Die.htm