The Collaborative International Dictionary of English v.0.48:

Cavesson \Cav"es*son\, Cavezon \Cav"e*zon\, n. [F. cave[,c]on,
   augm. fr. LL. capitium a head covering hood, fr. L. caput
   head. Cf. Caberzon.] (Man.)
   A kind of noseband used in breaking and training horses.
   [Written also caveson, causson.] --White.
   [1913 Webster]