promise vs understanding

promise

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 

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. 

understanding

noun
  • An informal contract; mutual agreement. 

  • Opinion, judgement or outlook. 

  • A reconciliation of differences. 

  • The act of one that understands or comprehends; comprehension; knowledge; discernment. 

  • Sympathy. 

  • Reason or intelligence, ability to grasp the full meaning of knowledge, ability to infer. 

adj
  • Showing compassion, tolerance, and forbearance. 

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