[posterboy]

While I talk hugely about language gone by, I have actually no idea what "rather" means. Take "rather obvious" as "I can't be the only one who'd consider this for a bit".

> For all we know

No, absolutely not. Rhymes are very important to old folk lore. And to language acquisition in general. And, in a metaphoric sense, to pattern matching over all.

Of course it is possible that the word was obscured from the get go lest it would appear derived. But I don't think it's onomatopoetic, if that's what you mean (I guess you didn't, though). Thinking about that, it's likely though that the word had to be pronounced by children, requiring easier phonemes, so perhaps no th. That gives a lot of leeway to speculate about an original root. Anther thought is that "swarz" (black) should be considered, because mines are inherently dirty, and as a kind of derogative. I agree though, expecting a single root would be too easy. A rhyme compressed into one word would easily obscure the term.

A very sad thought related to small people working in mines is child labor.