From Lakota America: A New History of Indigenous Power, by Pekka Hämäläinen (The Lamar Series in Western History; Yale U. Press, 2019), Kindle Loc. 96ff.
I use the word “Sioux” in this book as a cover term for seven related and allied people or oyátes: the Lakotas, Yanktons, Yanktonais, Mdewakantons [aka Mille Lacs Lake], Sissetons, Wahpetons, and Wahpekutes, who together formed the Očhéthi Šakówiŋ, the Seven Council Fires. Sioux is a French corruption of Ojibwe word “Nadouessioux” which means “snake” and thus enemy. Here I use Sioux when describing events or action that involve more than one or all peoples or oyátes; the alternative would have been to list each group in every instance. Although problematic, “Sioux” remains the most common English term used by Lakotas and non-Natives alike, and many modern Lakota oyátes identify themselves as Sioux tribes. “Dakota” is a cover term for the four eastern people, the Mdewakantons, Sissetons, Wahpetons, and Wahpekutes.
The spelling of Lakota words follows New Lakota Dictionary, edited and compiled by Jan Ullrich (2008; 2nd ed., Lakota Language Consortium, 2011). I have used Lakota names for the seven Lakota tribes or oyátes unless a French or English name is dominant in the literature: Hunkpapas (“head of camp circle entrance”), Minneconjous (“plant by water”), Oglalas (“scatter one’s own”), Sans Arcs (“without bows”), Sicangus (“burned thighs,” hence the French term Brulés), Sihasapas (“Blackfeet”), and Two Kettles (“two boilings”). As for other Native nations, I have used their preferred spellings of their names: Odawas rather than Ottawas; Mesquakies rather than Foxes; Wyandots rather than Hurons; and Ho-Chunks rather than Winnebagos.