The Collaborative International Dictionary of English v.0.48:

Cambist \Cam"bist\, n. [F. cambiste, It. cambista, fr. L.
   cambire to exchange. See Change.]
   A banker; a money changer or broker; one who deals in bills
   of exchange, or who is skilled in the science of exchange.
   [1913 Webster]

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

CAMBIST. A person skilled in exchange; one who deals or trades in promissory
notes or bills of exchange.