The Collaborative International Dictionary of English v.0.48:

Prisage \Pris"age\ (?; 48), n. [OF. prisage a praising, valuing,
   taxing; cf. LL. prisagium prisage; or from F. prise a taking,
   capture, prize. See Prize.] (O. Eng. Law)
   (a) A right belonging to the crown of England, of taking two
       tuns of wine from every ship importing twenty tuns or
       more, -- one before and one behind the mast. By charter
       of Edward I. butlerage was substituted for this.
       --Blackstone.
   (b) The share of merchandise taken as lawful prize at sea
       which belongs to the king or admiral.
       [1913 Webster]