improbability vs possibility

improbability

noun
  • The quality or state of being improbable; unlikelihood. 

  • That which is improbable; an improbable event or result. 

possibility

noun
  • The quality of being possible. 

  • An option or choice, usually used in context with future events. 

  • A thing possible; that which may take place or come into being. 

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