What is "whistle dixie"

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.

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

vb. (context idiomatic Southern US English) To engage in idle conversational fantasies.