Ugh, never mind. Misread the post.It was called Lac Aux Claies by the French until they renamed it after Simcoe, who is not an entirely unsympathetic figure. He abolished slavery in Upper Canada.
Of course the First Nations had many names for many parts of it that were used for thousands of years before the white people discovered.
Couchiching was one name - which is still in use and is a song by Gordon Iightfoot