feeble vs senescent

feeble

adj
  • Lacking force, vigor, or effectiveness in action or expression; faint. 

  • Deficient in physical strength. 

senescent

adj
  • Characteristic of old age. 

  • That ceases to divide. 

  • Growing old; decaying with the lapse of time. 

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