knock on wood vs look upon

knock on wood

verb
  • To take a customary action to ward off some misfortune that is believed to be attracted by a presumptuous statement. 

intj
  • Hopefully; a self-directive to undertake the customary action to ward off bad luck. 

look upon

verb
  • To consider or regard something in a specific manner. 

  • To gaze at something; to look on. 

How often have the words knock on wood and look upon occurred in a corpus of books? (source: Google Ngram Viewer )