Source : Webster's Revised Unabridged Dictionary (1913)

Mackinaw blanket \Mack"i*naw blan"ket\, Mackinaw \Mack"i*naw\
   [From Mackinac, the State of Michigan, where blankets and
   other stores were distributed to the Indians.]
   A thick blanket formerly in common use in the western part of
   the United States.

Source : WordNet®

mackinaw
     n 1: a short plaid coat made of made of thick woolen material
          [syn: {Mackinaw coat}]
     2: a thick plaid blanket formerly used in the northwestern
        United States [syn: {Mackinaw blanket}]
     3: a flat-bottomed boat used on upper Great Lakes [syn: {Mackinaw
        boat}]
     4: a heavy woolen cloth heavily napped and felted, often with a
        plaid design