mitigate vs weaken

mitigate

verb
  • To reduce, lessen, or decrease; to make less severe or easier to bear. 

  • To downplay. 

weaken

verb
  • To make weaker or less strong. 

  • To become weaker or less strong. 

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