The Collaborative International Dictionary of English v.0.48:

Callot \Cal"lot\, n.
   A plant coif or skullcap. Same as Calotte. --B. Jonson.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Calotte \Ca*lotte"\, Callot \Cal"lot\, n. [F. calotte, dim. of
   cale a sort of flat cap. Cf. Caul.]
   A close cap without visor or brim. Especially:
   (a) Such a cap, worn by English serjeants at law.
   (b) Such a cap, worn by the French cavalry under their
       helmets.
   (c) Such a cap, worn by the clergy of the Roman Catholic
       Church.
       [1913 Webster]

   To assume the calotte, to become a priest.
      [1913 Webster]