The Collaborative International Dictionary of English v.0.48:

Loo \Loo\ (l[=oo]), n. [For older lanterloo, F. lanturelu,
   lanturlu, name of the game; orig., the refrain of a
   vaudeville.]
   (a) An old game played with five, or three, cards dealt to
       each player from a full pack. When five cards are used
       the highest card is the knave of clubs or (if so agreed
       upon) the knave of trumps; -- formerly called
       lanterloo.
   (b) A modification of the game of "all fours" in which the
       players replenish their hands after each round by drawing
       each a card from the pack.
       [1913 Webster]

   Loo table, a round table adapted for a circle of persons
      playing loo.
      [1913 Webster]