poster child vs quintessence

poster child

noun
  • One who is a prototypical or quintessential example of something. 

quintessence

noun
  • A thing that is the most perfect example of its type; the most perfect embodiment of something; epitome, prototype. 

  • A pure substance. 

  • The fifth alchemical element, or essence, after earth, air, fire, and water that fills the universe beyond the terrestrial sphere. 

  • The essence of a thing in its purest and most concentrated form. 

  • A hypothetical form of dark energy postulated to explain observations of an accelerating universe. 

verb
  • To reduce to its purest and most concentrated essence. 

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