senile vs septuagenarian

senile

adj
  • Of, or relating to old age. 

  • Exhibiting the deterioration in mind and body often accompanying old age; doddering. 

septuagenarian

adj
  • Of or related to seventysomethings. 

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

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