[Opinions] Re: Native American Historical Fantasy Novel - Accuracy of Names
No, a Sioux (Lakota? Dakota? Oglalla? Not just Sioux.) would not have a name from another group. Even if some member of another tribe/group somehow became one of them, that person would take or be given a different name.
Don't try to make up a name; I mean, you can use English word names, like Little Buffalo or Spotted Hawk, if you want to. But don't try to make up names that sound like they could be Indian names, because it's like uttering some vaguely Italian-sounding sounds and calling it a made-up Italian name. The Sioux (and all the other groups) didn't just randomly give their kids or themselves pretty-sounding collections of sounds. Names were chosen carefully and often changed over a person's lifetime to reflect their experiences and achievements.
You don't have to be able to speak the language to name accurately; if you used English phrases as names, it would be understood by your readers that these pre-contact people weren't actually calling each other Little Buffalo or Spotted Hawk in English.
Just don't fall into the trap of a lot of young kids and try to put together first, middle and last names!
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Steve Martin