relapse vs turn back

relapse

verb
  • To fall back again; to slide or turn back into a former state or practice. 

  • To slip or slide back physically; to turn back. 

  • To return to a vice, especially self-harm or alcoholism, failing to maintain abstinence. 

  • To recur; to worsen, be aggravated (after a period of improvement). 

noun
  • An occasion when a person becomes ill again after a period of improvement 

  • The act or situation of relapsing. 

turn back

verb
  • To return to a previous state of being. 

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

  • To reverse direction and retrace one's steps. 

  • To prevent or refuse to allow passage or progress. 

  • To adjust to a previous setting. 

  • To fold something back; to fold down. 

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