certainty vs undertaking

certainty

noun
  • An instance of being certain. 

  • The state of being certain. 

  • A fact or truth unquestionably established. 

undertaking

noun
  • The act of one who undertakes (in either sense). 

  • A promise or pledge; a guarantee. 

  • That which is undertaken; any business, work, or project which a person engages in, or attempts to perform; an enterprise. 

  • The business of an undertaker, or the management of funerals. 

How often have the words certainty and undertaking occurred in a corpus of books? (source: Google Ngram Viewer )