enforce vs exempt

enforce

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

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

exempt

adj
  • Free from a duty or obligation. 

  • Not entitled to overtime pay when working overtime. 

verb
  • To grant (someone) freedom or immunity from. 

noun
  • One of four officers of the Yeomen of the Royal Guard, having the rank of corporal; an exon. 

  • One who has been released from something. 

  • A type of French police officer. 

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