This still doesn't make sense as "hellin" isnt a term in wide use. What makes the most sense is transition from "fuckin". But why not simply use fuckin? Surely invoking sex is less taboo than invoking hell.
> What makes the most sense is transition from "fuckin". But why not simply use fuckin?
Indeed, you have a community that wants to be family friendly but high energy, and so the technique is to start with "fucking", one of the top tier swears, and replace its root word with the lowest tier swears. And part of the charm is that "hell" is barely a taboo topic -- it's part of the Apostle's creed and plenty of sermons, and there's no commandment against its use[1], yet it gets minced to "heck"!
Etymology
From heck as a euphemism for hell.