knock on wood vs point the finger at

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. 

point the finger at

verb

  • To accuse or blame (someone). 

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