cynosure vs polar star

cynosure

noun
  • That which serves to guide or direct; a guiding star. 

  • Ursa Minor or Polaris, the North Star, used as a guide by navigators. 

  • Something that is the center of attention; an object that serves as a focal point of attraction and admiration. 

polar star

noun
  • Synonym of pole star 

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