augur vs knock on wood

augur

verb
  • To foretell events; to exhibit signs of future events; to indicate a favorable or an unfavorable outcome. 

noun
  • A diviner who foretells events by the behaviour of birds or other animals, or by signs derived from celestial phenomena, or unusual occurrences. 

  • An official who interpreted omens before the start of public events. 

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