grizzled vs septuagenarian

grizzled

adj
  • streaked or mixed with grey; grizzly; griseous 

  • greyed, old 

  • grey or partly grey 

septuagenarian

adj
  • Of or related to seventysomethings. 

noun
  • Synonym of seventysomething: a person between 70 and 79 years old. 

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