The story
From the French name of the nearby Rivière des Moines, which superficially means "river of the monks" and has traditionally been interpreted as a reference to the Trappist monks who settled along it. "It is more likely, however, to be a name of Native American origin, recorded in a 1673 text as moinguena", a Miami designation of the Moingona. The precise interpretation is uncertain; see Moingona.
Etymology from Wiktionary, CC BY-SA 4.0.