be whistling Dixie

proverb slang To have an unrealistic, usually overly optimistic, view of something. "Dixie" was a song popular among Confederate soldiers during the US Civil War and became associated with continuing to hope for the success of a lost cause. Primarily heard in UK. You're whistling Dixie if you think we're making the playoffs this year. Please, there's no way they give everyone a raise this year. You're just whistling Dixie, Bob!