The Collaborative International Dictionary of English v.0.48:

peacoat \pea"coat`\, pea coat \pea" coat`\(p[=e]"k[=o]t`), n.
   [Prob. fr. D. pij, pije, a coat of a coarse woolen stuff.]
   A thick loose double-breasted woolen jacket, or coat,
   commonly worn by sailors in cold weather; a pea-jacket.

   Syn: pea coat, peacoat, pea jacket, peajacket, pea-jacket.
        [1913 Webster+ WordNet 1.5]