assert vs vow

assert

verb
  • To maintain or defend, as a cause or a claim, by words or measures; to vindicate a claim or title to 

  • He would often assert that there was life on other planets. 

  • To insist on the legitimacy of one's rights, opinion, etc; not to allow oneself to be dismissed; to ensure that one is taken into consideration; to make oneself respected; to be assertive. 

  • To use or exercise and thereby prove the existence of. 

  • To set a signal on a line using a voltage or electric current. 

  • To specify that a condition or expression is true at a certain point in the code. 

  • To declare with assurance or plainly and strongly; to state positively. 

noun
  • an assertion; a section of source code which tests whether an expected condition is true. 

vow

verb
  • To declare publicly that one has made a vow, usually to show one's determination or to announce an act of retaliation. 

  • To make a vow; to promise. 

  • To make a vow regarding (something). 

noun
  • A solemn promise to perform some act, or behave in a specified manner, especially a promise to live and act in accordance with the rules of a religious order. 

  • A declaration or assertion. 

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