importance vs must-have

importance

noun
  • Something of importance. 

  • The quality or condition of being important or worthy of note. 

  • personal status or standing. 

  • significance or prominence. 

must-have

noun
  • An item that one must own, or a feature that is essential to a service, etc. 

adj
  • Essential to own. 

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