aggravate vs gain strength

aggravate

verb
  • To exasperate; to provoke or irritate. 

  • To make (an offence) worse or more severe; to increase in offensiveness or heinousness. 

  • To make worse; to exacerbate. 

gain strength

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