Twila

The individual claiming that the name is of Sioux origin is wrong about almost everything they said.
They don't even know the historical range of the Lakota people (the people that are typically called Sioux) as the only state they listed that had a significant historical Lakota population coinciding with white settlement was Iowa-- not Illinois, Missouri, Tennessee, or Kentucky. They were located in the region around Lake Superior when Europeans arrived and were eventually pushed into the Great Plains. They may have lived in the other listed states at an earlier point in history, but that would be irrelevant to this argument because it did not coincide with white settlement and thus, obviously, no names could have been passed into white society at those times. So the regional analysis does not check out at all.
They also claim the name means "two ponies" in the Lakota language, which is a suspicious claim to make about such a short name, especially since Native American names and words tend to be LONGER than English ones not shorter, but of course, it is easily proven entirely wrong as the Lakota word for horse is in fact šúŋkawakȟáŋ. This is a word that literally means "dog of power," as horses are of course not indigenous to North America and thus many words for them in various Native American languages are combinations of existing words. This is also another reason that this commentor's regional analysis makes no sense, because in the points in history when the Lakota would have lived in the states they listed, they not only wouldn't have had contact with settlers but also would not have had contact with horses yet either.
It is possible that this name has some indigenous origin, but I would not take the word of someone whose only source is their acquaintance's grandma's friend and who seems to have no knowledge of the culture and history they're evoking, let alone even a willingness to double-check what they think they know. This is especially bothersome to me as indigenous people are struggling in this country to preserve knowledge and history for future generations, and indigenous cultures are routinely appropriated and misrepresented, as if genocide wasn't enough.
Please, I urge everyone, if you hear someone who is not definitively indigenous claim to know some hidden information about indigenous history or language: find some other, backed-up sources before believing or repeating them. And honestly, everyone could benefit from learning more indigenous history to begin with, before it's even a problem.