agonize vs rub salt in the wound

agonize

verb
  • To cause agony or anguish in someone. 

  • To writhe with agony; to suffer violent anguish. 

  • To struggle; to wrestle; to strive desperately, whether mentally or physically. 

rub salt in the wound

verb
  • To make an injury, physical or emotional, feel worse. 

How often have the words agonize and rub salt in the wound occurred in a corpus of books? (source: Google Ngram Viewer )