portend vs promise

portend

verb
  • To signify; to denote. 

  • To serve as a warning or omen of. 

promise

verb
  • To commit to (some action or outcome), or to assure (a person) of such commitment; to make an oath or vow. 

  • To give grounds for expectation, especially of something good. 

noun
  • A transaction between two persons whereby the first person undertakes in the future to render some service or gift to the second person or devotes something valuable now and here to his use. 

  • A placeholder object representing the eventual result of an asynchronous operation. 

  • Reason to expect improvement or success; potential. 

  • an oath or affirmation; a vow 

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