imbecility vs youngness

imbecility

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

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

youngness

noun
  • The state or qualities of being young or youthful; youth. 

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