Poker is a structured game with many rules and regulations; on top of this, players are expected to act properly and follow established etiquette.
One such etiquette rule that applies at the poker table is leaving your money on the table until you decide to leave. "Going south" is the term used to describe when a player will take cash off the table, with or without the other players knowing, and it is highly frowned upon. In fact, it is usually prohibited in most casinos and card rooms.