What does "loo" mean?

Loo: (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. Loo table, a round table adapted for a circle of persons playing loo.