Western Siouan languages
The Western Siouan languages, also called Siouan proper or simply Siouan, are a large language family native to North America. They are closely related to the Catawban languages, sometimes called Eastern Siouan, and together with them constitute the Siouan (Siouan–Catawban) language family.
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.