The truth behind Des Moines

There are a lot of cities in the US with French names (Fond du Lac, Eau Claire, Terre Haute) as well as French-Indian names like Algonquin and Cheyenne. One city that comes to mind is Des Moines. Now, I can't say that I ever gave much thought to this city, but in the back of my mind I always figured it referred to monks. Turns out that Des Moines too is a French-Indian name, and maybe even a huge practical joke played by the Indians.
Source: Des Moines Register - Is 'Des Moines' just some dirty joke?

More: French in the news, 2000 to 2009