elderly vs septuagenarian

elderly

noun
  • Older people as a whole. 

  • An elderly person. 

adj
  • old; having lived for relatively many years. 

  • Of an object, being old-fashioned or frail due to aging. 

septuagenarian

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

adj
  • Of or related to seventysomethings. 

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