infirmity vs weakness

infirmity

noun
  • a moral weakness or defect 

  • feebleness, frailty or ailment, especially due to old age. 

weakness

noun
  • The condition of being weak. 

  • An inadequate quality; fault 

  • A special fondness or desire. 

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