persist vs stay the course

persist

verb
  • To continue to exist. 

  • To go on stubbornly or resolutely. 

  • To repeat an utterance. 

  • To cause to persist; make permanent. 

stay the course

verb
  • To persist or continue. 

How often have the words persist and stay the course occurred in a corpus of books? (source: Google Ngram Viewer )