commend vs impugn

commend

verb
  • To recommend. 

  • To entrust or commit to the care of someone else. 

  • To praise or acclaim. 

  • To mention by way of courtesy, implying remembrance and goodwill. 

  • To congratulate or reward. 

impugn

verb
  • To verbally assault, especially to argue against an opinion, motive, or action; to question the truth or validity of. 

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