knock on wood vs scorn

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. 

scorn

verb
  • To scoff, to express contempt. 

  • To feel or display contempt or disdain for something or somebody; to despise. 

  • To refuse to do something, as beneath oneself. 

  • To reject, turn down. 

noun
  • A display of disdain; a slight. 

  • Contempt or disdain. 

  • An object of disdain, contempt, or derision. 

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