I actually googled that one, because I was 100% sure that the answer is "Indian". I've never seen the name written in English before. The translation in my mother tongue was also just "The Indian Joe". One new thing I learned today. :)
That's interesting to learn that translations use the local language's term for "Indian" or "aborigine" rather than the colloquial/ephithet slang of Twain.
Yeah but in fiction it's a bit more complicated. Character names are often chosen for their meaning or sound, so the translator has to decide whether to lose the meaning or maybe describe it in footnotes, or to create a corresponding name in target language. The latter happens more often in children's literature, or fantasy (Harry Potter, LOTR, Disney ...).