Going South

The phrase "going south" to mean "becoming worse" is another one whose origin is not settled.

The most common origin attributes it to the standard orientation of maps. South is the downwards direction so things going south are going down. That would fit this type of usage: "Yesterday the stock market moved south, ending up on a loss for the day."

Another origin say that it was a euphemism used by some Native Americans for dying. "He was unconcerned that his health might go south."

This idiom always means that a situation becomes unfavorable, decreases, or takes a turn for the worse. "My luck went south."