feedforward vs knock on wood

feedforward

verb
  • To respond in advance 

noun
  • An anticipatory response to expected changes in the environment of a system 

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 feedforward and knock on wood occurred in a corpus of books? (source: Google Ngram Viewer )