Wikipedia
The historic Miami-Illinois people who are today referred to as the Moingona or Moingwena were close allies of or perhaps part of the Peoria. They were assimilated by that tribe and lost their separate identity about 1700. The name "Moingona" was probably the basis for the name of the City of Des Moines, the Des Moines River, and Des Moines County, Iowa.
Jacques Marquette documented in 1672 that the Peolualen (the modern Peoria). and the mengakonkia (Moingona) were among the Ilinoue ( Illinois) tribes who all "speak the same language." Other names for them mentioned in 1672-73 records were "Mengakoukia," and "Mangekekis."
In 1673 Marquette and Louis Jolliet left their canoes and followed a beaten path away from the river out onto the prairie to three Illinois villages within about a mile and a half of each other. Marquette identified only one of the villages at the time, the peouarea, but a later map apparently by him identified another as the Moingwena. He said of the 1673 meeting that there was "some difference in their language," but that "we easily understood each other."
Father Jacques Gravier reports helping the close allies "Peouaroua and Mouingoueña" deal with a common adversary in 1700.
Pierre François Xavier de Charlevoix, a missionary who explored the region in 1721, recorded that "le Moingona" was "an immense and magnificent Prairie, all covered with Beef and other Hoofed Animals." He italicized the term to indicate it was a geographical term and noted that "one of the tribes bears that name." Charlevoix was a professor or belles lettres, and his spelling has come to be a preferred spelling in general and scholarly discussions.