The Collaborative International Dictionary of English v.0.48:

Cotta \Cot"ta\, n. [LL. See Coat.]
   1. (Eccl.) A surplice, in England and America usually one
      shorter and less full than the ordinary surplice and with
      short sleeves, or sometimes none.
      [Webster 1913 Suppl.]

   2. A kind of very coarse woolen blanket.
      [Webster 1913 Suppl.]