imbecility vs insanity

imbecility

noun
  • Something imbecilic; a stupid action, behaviour, etc. 

  • The quality of being imbecile; weakness; feebleness, especially of mind. 

insanity

noun
  • The state of being insane; madness. 

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