The Going South poker term refers to the action of taking the chips off of the table during a cash game, most often to reduce the risk.
At the very least, this move is unethical and a demonstration of poor poker etiquette. At the worst, it is illegal, and the player that does it will likely get banned from the poker room.
For example, let’s say it’s the last betting round, and there’s only you and one other player left. Your opponent makes an all-in bet but not before removing half of their chips from the table first.
Effectively, they are still putting you in a tough spot to call, but they wanted to protect half of their stake by Going South just in case.