Siouan languages
Siouan or Siouan–Catawban is a language family of North America that is located primarily in the Great Plains, Ohio and Mississippi valleys and southeastern North America with a few other languages in the east.
Mandan
The English name "Mandan" is derived from the French-Canadian explorer Pierre Gaultier, Sieur de la Verendrye, who in 1738 heard it as "Mantannes" from his Assiniboine guides, which call the Mandan "Mayádąna". He had previously heard the earth lodge peoples referred to by the Cree as "Ouachipouennes", "the Sioux who go underground". The Assiniboine are Siouan speakers. Nearby Siouan speakers had exonyms similar to "Mantannes" in their languages, for instance, Teton "Miwáthaŋni" or "Miwátąni", Yanktonai "Miwátani", Yankton "Mawátani" or "Mąwátanį", Dakota "Mawátąna" or "Mawátadą", etc.