centenarian vs eldern

centenarian

adj
  • Aged 100 years or more; extremely old. 

  • Of or relating to centenarians or a centenary celebration. 

noun
  • One who or that which is at least 100 years old. 

eldern

adj
  • Elder; elderly; aged; old. 

  • Not new; old; ancient. 

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