forestall vs knock on wood

forestall

verb
  • To anticipate, to act foreseeingly. 

  • To obstruct or stop up, as a road; to stop the passage of a highway; to intercept on the road, as goods on the way to market. 

  • To preclude or bar from happening, render impossible. 

  • To prevent, delay or hinder something by taking precautionary or anticipatory measures; to avert. 

  • To deprive (with of). 

noun
  • Something situated or placed in front. 

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