hang on vs seize upon

hang on

verb
  • To hold, grasp, or grip. 

  • To pay close attention to, or regard with (possibly obsequious) admiration. 

  • To depend upon. 

  • To keep; to store something for someone. 

  • To continually believe in something; to have faith in. 

  • To wait a moment. 

  • To persevere. 

seize upon

verb
  • To grasp or take hold of (an object) suddenly, forcibly, or tightly. 

  • To take up, embrace, enact, or turn eagerly to (a plan, idea, ideology, cause, practice, method, etc.); to grasp, understand, and accept quickly; to adopt wholeheartedly or vigorously. 

  • To take possession of or claim (an idea, person, event, etc.) as one's own; to assimilate, absorb, annex, co-opt. 

How often have the words hang on and seize upon occurred in a corpus of books? (source: Google Ngram Viewer )