The Collaborative International Dictionary of English v.0.48:

Cosenage \Cos"en*age\ (k?z"'n-?j), n.
   See Cozenage.
   [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

COSENAGE, torts. Deceit, fraud: that kind of circumvention and wrong, which
has no other specific name. Vide Ayl. Pand. 103 Dane's Ab. Index, h.t.