deteriorate vs turn back

deteriorate

verb
  • To make worse; to make inferior in quality or value; to impair. 

  • To grow worse; to be impaired in quality; to degenerate. 

turn back

verb
  • To prevent or refuse to allow passage or progress. 

  • To cause to reverse direction and retrace one's steps. 

  • To return to a previous state of being. 

  • To reverse direction and retrace one's steps. 

  • To adjust to a previous setting. 

  • To fold something back; to fold down. 

How often have the words deteriorate and turn back occurred in a corpus of books? (source: Google Ngram Viewer )