'when it was his turn to add his name to the document, the Indian Agent heard him say “nothing.” '  I understand your frustration about others misinterpreting your name.  My grandfather had the same problem when he arrived in Canada.  Fortunately, there is an easy and inexpensive remedy to change your name to whatever you want though the courts.  I did it years ago through the legal aid facility at U of T.  Something you might want to check out.