knock on wood vs postulate

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. 

postulate

verb
  • To assume as a truthful or accurate premise or axiom, especially as a basis of an argument. 

  • To appoint or request one's appointment to an ecclesiastical office. 

adj
  • Postulated. 

noun
  • An axiom. 

  • Something assumed without proof as being self-evident or generally accepted, especially when used as a basis for an argument. Sometimes distinguished from axioms as being relevant to a particular science or context, rather than universally true, and following from other axioms rather than being an absolute assumption. 

  • A requirement; a prerequisite. 

  • A fundamental element; a basic principle. 

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