avoid vs knock on wood

avoid

verb
  • To try not to do something or to have something happen 

  • To stay out of the way of (something harmful). 

  • to keep away from; to keep clear of; to stay away from 

  • To try not to meet or communicate with (a person); to shun 

  • To make void, to annul; to refute (especially a contract). 

  • To defeat or evade; to invalidate. 

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