"pertaining to the Sioux," 1885, from Sioux + -an. Replacing Dakotan.
Entries linking to siouan
Sioux
in reference to a family or group of North American native peoples, 1761, from North American French, short for Nadouessioux, sometimes said to be from Ojibway (Algonquian) Natowessiwak (plural), literally "little snakes," from nadowe "Iroquois" ("(big) snakes"). Another explanation traces it to early Ottawa (Algonquian) singular /na:towe:ssi/ (plural /na:towe:ssiwak/) "Sioux," apparently from a verb meaning "to speak a foreign language" [Bright]. In either case, a name given by their neighbors; the people's name for themselves is Dakota.
-an
word-forming element meaning "pertaining to," from Latin -anus, adjective suffix, in some cases via French -ain, -en. From PIE *-no-.