In a previous post about the stereotyped Indian utterances “how” and “ugh,” I noted that “how” appears to be derived from the Muskogee Creek word hvo (pronounced “haw”).
I could be wrong. Back in 1986, Cecil Adams of The Straight Dope argued for another group of American Indian languages. Someone had asked Adams whether Indians ever really used “how” as a greeting. He replied that no, they didn’t, but that in several Siouan languages of the Great Plains (Lakota, Dakota, and Omaha), there is a word that serves as “a sort of all-purpose introductory adverb or interjection.” That word is variously spelled ho, hao, hau, or howo.
The resemblance to Creek hvo, another multi-purpose affirmative interjection, is striking. Even though the Creek language is only distantly related to the Siouan languages, much like English is related to Persian.
But wait a minute, I hear you saying. Cecil Adams is just this guy who churns out snarky columns for “alternative” newspapers. A self-appointed know-it-all. Why are you taking him seriously?
OK, there are some mistakes in Adams’ answer. He described the Siouan language family as a single “major language” with many “versions.” He called Lakota the language of “the Tetons,” which is rather quaint. And I did wonder why he investigated only Siouan languages, the ones spoken by the guys with the war bonnets and tepees.
Well, if you’re on a deadline, I guess that was the likeliest place to look. And Adams did claim to base his answer on readings of not only language dictionaries, but also transcribed Siouan tales in their original languages.
But my main reason for accepting Cecil Adams’s info is that I don’t know jack about the Siouan languages myself. I still prefer my theory that Creek hvo is the likeliest source for “how,” because the Creeks were the largest Indian polity on the U.S. border from the Revolution to the 1830s (when they were deported to Indian Territory in modern Oklahoma). But what if the “how” stereotype didn’t emerge until, say, the 1850s, or after the Civil War? As one of the so-called “Five Civilized Tribes,” the Creeks in Oklahoma would be less likely to have shaped a stereotype associated with Indians of the “Wild West.”
Adams continues: Because a word like “how” occurred so often at the beginning of Siouan speeches, “ignorant pioneers” concluded that the word was an “Indian greeting.” Popular culture, with a major boost from Hollywood westerns, finally transformed it into a universal Indian greeting, preferably delivered by a Big Chief in a feathered headdress.
So the next step in pursuing the history of “how” must be to collect and date examples of its use in literature and popular culture. This cannot be easily done with database searches because “how” is a homograph of one of the most common adverbs in the English language.
P.S. The Oxford American Dictionary (I haven’t yet checked the OED) dates how (“used in humorous imitation” of North American Indians) from the early 19th century — “perhaps from Sioux háo or Omaha hou.” Have they been reading Cecil Adams? Anyway, the earlier the derivation, the more likely it will have been derived from Muskogee.
à la Rob 
There is so much scholarship out there that, for whatever reason or another, has never reached common understanding. I wonder why that is.
My cousin, an ancient alien fanatic told me that on that show some “historian” claimed that Hau wasn’t a greeting, but that when they raised their hand they were showing that they only had 5 fingers instead of 6, as some strange beings had.
…13 years of public education erased and replaced by a few programs on the [alternative] History Channel.