doddering vs senescent

doddering

adj
  • mentally or physically infirm due to old age; senile 

noun
  • A shaking or trembling movement, as of old age. 

senescent

adj
  • Characteristic of old age. 

  • That ceases to divide. 

  • Growing old; decaying with the lapse of time. 

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