[Opinions] Re: Native American Historical Fantasy Novel - Accuracy of Names
I am a non-Indigenous individual, so take what I say with a grain of salt. I am also a writer however, and have included First Nations peoples in my work. I would highly suggest trying to get in contact with someone from the Sioux nation that you are writing about, they may be able to help you with finding resources and answer some of your questions.
My gut feeling, (again, not Indigenous) is that making up names might not be such a great idea unless you are really familiar with the elements of Siouan language and the elements that would have gone into making a name.
If you do contact someone for help with your research, always remember to compensate your sensitivity readers!