modify vs persist

modify

verb
  • To be or become modified. 

  • To change part of. 

  • To set bounds to; to moderate. 

  • To qualify the meaning of. 

persist

verb
  • To go on stubbornly or resolutely. 

  • To repeat an utterance. 

  • To cause to persist; make permanent. 

  • To continue to exist. 

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