ageing vs centenarian

ageing

adj
  • UK, Australia, and New Zealand standard spelling of aging. 

noun
  • UK, Australia, and New Zealand standard spelling of aging. 

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. 

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