ninetysomething vs septuagenarian

ninetysomething

noun
  • A person between 90 and 99 years old. 

num
  • An indeterminate value between 90 (inclusive) and 100 (exclusive). 

septuagenarian

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

adj
  • Of or related to seventysomethings. 

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