Representing an earlier colloquial pronunciation of Mackinac, a strait between Lake Huron and Lake Michigan, an island in the strait, and an important trading-post on the island; ultimately from Ojibwe mishinii-makinaang (“at the place of many snapping turtles”).
mackinaw (plural mackinaws)
- A heavy, woolen cloth.
- A blanket made of wool formerly distributed to the Amerindians by the U.S. government.
- A cargo boat, with a large flat bottom and sharp ends, formerly used on the Great Lakes and the Missouri River (to a lesser extent, elsewhere).
- A schooner-rigged boat once used on the Great Lakes.
See also 
- Merriam-Webster's Collegiate Dictionary: Tenth Edition (1997)