go from bad to worse vs go south

go from bad to worse

verb
  • to become even worse 

go south

verb
  • To become unfavorable; to decrease; to take a turn for the worse. 

  • To make an escape; to disappear. 

  • To give somebody oral sex. 

How often have the words go from bad to worse and go south occurred in a corpus of books? (source: Google Ngram Viewer )