Source : Webster's Revised Unabridged Dictionary (1913)

Cajun \Ca"jun\, n. [A corruption of {Acadian}.] (Ethnol.)
   In Louisiana, a person reputed to be Acadian French descent.

Source : WordNet®

Cajun
     n : a Louisianian descended from Acadian immigrants from Nova
         Scotia (`Cajun' comes from `Acadian')