benign vs mitigatory

benign

adj
  • Not posing any serious threat to health; not particularly aggressive or recurrent. 

  • Not harmful to the environment. 

  • Kind; gentle; mild. 

  • mild and favorable 

mitigatory

adj
  • reducing, lessening the effects of something, generally something painful or uncomfortable 

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