hat money

from The Collaborative International Dictionary of English v.0.48

Primage \Pri"mage\ (?; 48), n. [F.] (Com.)
   A charge in addition to the freight; originally, a gratuity
   to the captain for his particular care of the goods
   (sometimes called {hat money}), but now belonging to the
   owners or freighters of the vessel, unless by special
   agreement the whole or part is assigned to the captain.
   --Homans.
   [1913 Webster]

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

HAT MONEY, mar. law. The name of a small duty paid to the captain and 
mariners of a ship, usually called primage. (q.v.)