enforce vs expunge

enforce

verb
  • To keep up, impose or bring into effect something, not necessarily by force. 

  • To give strength or force to; to affirm, to emphasize. 

expunge

verb
  • To erase or strike out. 

  • To eliminate completely; to annihilate. 

  • To delete permanently (e-mail etc.) that was previously marked for deletion but still stored. 

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