improbability vs likeliness

improbability

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

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

likeliness

noun
  • The condition or quality of being probable or likely to occur. 

  • Likeness; similarity. 

  • Suitability; agreeableness. 

  • Likelihood, probability or chance of occurrence; plausibility or believability. 

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