feebleness vs senility

feebleness

noun
  • The quality or state of being feeble; debility; infirmity. 

senility

noun
  • The losing of memory and reason due to senescence. 

  • Senescence; the bodily and mental deterioration associated with old age. 

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