cap it all off vs rub salt in the wound

cap it all off

verb
  • To surpass or outdo something. 

  • To finish or complete something; to add a finishing touch. 

rub salt in the wound

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

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