From WordNet (r) 3.0 (2006) [wn]:
Cajun
n 1: a Louisianian descended from Acadian immigrants from Nova
Scotia (`Cajun' comes from `Acadian')
From The Collaborative International Dictionary of English v.0.48 [gcide]: Cajun \Ca"jun\, n. [A corruption of Acadian.] (Ethnol.) In Louisiana, a person reputed to be Acadian French descent. Also used attributively, as in Cajun cooking. [Webster 1913 Suppl. +PJC]