depend vs knock on wood

depend

verb
  • To be contingent or conditioned; to have something as a necessary condition; to hinge on. 

  • To hang down; to be sustained by being fastened or attached to something above. 

  • To trust; to have confidence; to rely. 

  • To cause to be contingent or dependent on; to set as a necessity. 

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