Wordorigins.org

The name Wisconsin is of Algonquin origin. The exact dialect and meaning are lost, however. The name was originally applied to the Wisconsin River and then extended to the surrounding territory. The French recorded the name as Ouisconsin and from this was altered into its familiar English form.

Various hypotheses about the origin exist. It could be from the Ojibwa wishkonsing, or place of the beaver (or muskrat). Other hypotheses include the belief that it means “gathering of waters” in one dialect or another.

(Sources: Illustrated Dictionary of Place Names; Webster’s Third New International Dictionary)