Well, I could not help but think of stereotypes. I'd never seen an Indian say "How!" for real before.
Did Indians ever really say "how" in formal greeting? --Keath G., Baton Rouge, Louisiana
Not exactly, but you've hit on one of those rare bits of frontier rubbish that actually has some basis in fact. There is no such thing as a universal Indian greeting--the original inhabitants of North America spoke some 500 different languages--but we do find variants of "how" in the native speech of many Plains Indians tribes, who spoke versions of a major language called Siouan. The Tetons said "howo" and "ho," the Dakota had "hao" and "ho," and the Omaha had "hau" (and maybe "ho" too, but I didn't find it in my Omaha dictionary).
Below: "How, paleface! Stop in and buy some trinkets."