demonstrate vs swear to

demonstrate

verb
  • to show, display, or present; to prove or make evident 

  • to show the steps taken to create a logical argument or equation. 

  • to show how to use (something). 

  • to participate in or organize a demonstration. 

swear to

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