whistle dixie

from The Collaborative International Dictionary of English v.0.48

Dixie \Dix"ie\ (d[i^]ks"[y^]), prop. n.
   1. A colloquial name for the Southern portion of the United
      States, esp. during the Civil War. [U.S.]

   Syn: Dixieland, Dixie Land, the Confederacy, Confederate
        States of America, the South.

   Syn: . [1913 Webster]

   2. a song popular in the Confederate states during the
      American Civil War, and still played as a nostalgic anthem
      by those patriotic to the American south. It was written
      by Daniel D. Emmett in 1859.
      [PJC]

   {whistle Dixie} to talk unrealistically; to engage in
      unrealistic or overoptimistic fantasies; as, that ain't
      just whistlin' Dixie.
      [PJC]