deem vs knock on wood

deem

verb
  • To hold in belief or estimation; to adjudge as a conclusion; to regard as being; to evaluate according to one's beliefs; to account. 

  • To think, judge, or have or hold as an opinion; to decide or believe on consideration; to suppose. 

noun
  • An opinion, a judgment, a surmise. 

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. 

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