Siouan languages
Siouan languages can be grouped into the Western Siouan languages and Catawban languages. The Western Siouan languages can be divided into Missouri River languages (such as Crow and Hidatsa), Mandan, Mississippi River languages (such as Dakotan, Chiwere-Winnebago, and Dhegihan languages), and Ohio Valley Siouan branches. The Catawban languages consist only of Catawban and Woccon.
Sioux
The name "Sioux" was adopted in English by the 1760s from French. It is abbreviated from "Nadouessioux", first attested by Jean Nicolet in 1640. The name is sometimes said to be derived from an Ojibwe exonym for the Sioux meaning "little snakes" (compare "nadowe" "big snakes", used for the Iroquois). The spelling in "-x" is due to the French plural marker.
The Proto-Algonquian form "*na·towe·wa", meaning "Northern Iroquoian", has reflexes in several daughter languages that refer to a small rattlesnake (massasauga, "Sistrurus"). An alternative explanation is derivation from an (Algonquian) exonym " na·towe·ssiw" (plural " na·towe·ssiwak"), from a verb "*-a·towe·" meaning "to speak a foreign language". The current Ojibwe term for the Sioux and related groups is "Bwaanag" (singular "Bwaan"), meaning "roasters". Presumably, this refers to the style of cooking the Sioux used in the past.