The Collaborative International Dictionary of English v.0.48:

Croupier \Crou"pi*er\ (kr[=oo]"p[i^]*[~e]r), n. [F.; prop., one
   who sits on the croup, and hence, in the second place; an
   assistant. See 1st Croup.]
   1. One who presides at a gaming table and collects the
      stakes.
      [1913 Webster]

   2. One who, at a public dinner party, sits at the lower end
      of the table as assistant chairman.
      [1913 Webster]

WordNet (r) 3.0 (2006):

croupier
    n 1: someone who collects and pays bets at a gaming table