Dixie, also known as Dixieland, is a nickname for a region of the Southern United States. There is no official definition of the area of this region, but most include the states which belonged to the Confederate States of America (1860–65).

The origin of the word is disputed.

According to the most common explanation of the name, $10 notes issued before 1860 by the Citizens’ Bank of New Orleans and used largely by French-speaking residents were imprinted with dix (French: “ten”) on the reverse side—hence the land of Dixies, or Dixie Land, which applied to Louisiana and eventually the whole South.

Source : Encylopaedia Britannica

Another theory suggests that it may be derived from Jeremiah Dixon, one of the surveyors of the Mason–Dixon Line, which defined the border between Maryland and Pennsylvania.