relent vs show the white flag

relent

noun
  • Stay; stop; delay. 

verb
  • To slacken; to abate. 

  • To give in or be swayed; to become less hard, harsh, or cruel; to show clemency. 

show the white flag

How often have the words relent and show the white flag occurred in a corpus of books? (source: Google Ngram Viewer )