The name Des Moines turns out to be an insult.
Here is, verbatim, the entry for "Des Moines" in the authoritative and academic "Native American Placenames of the United States":
From French Rivière des Moines, which could be interpreted as 'river of the monks' or 'river of the mills.' In fact, however, Moines is here an abbreviation used by the French for Moingouena (Eng. Moingwena), an Algonquian subgroup (Vogel 1983). The Native American term is /mooyiinkweena/, and it was a derogatory name applied to the Moingouenas by the Peorias, another subgroup. Its meaning, as an early French writer said is, 'visage plein d'ordure' -- or in plain English 'shit-face' (Costa 2000:45)
From the comments, an even more dismissive factoid:
Iowa was first the name given to the Indians who lived in that region, but as is often the case, the whites got the name from the next tribe up the line, who had an unflattering word for their neighbors. Not as bad as "shit-faces" in this case, but it meant "sleepy ones.
No wonder the Iowa caucuses make them bonkers. They're probably already seriously annoyed.