forecast vs knock on wood

forecast

verb
  • To foreshadow; to suggest something in advance. 

  • To estimate how something will be in the future. 

noun
  • exacta 

  • An estimation of a future condition. 

  • A prediction of the weather. 

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