dissimilarity vs selfsameness

dissimilarity

noun
  • Lack of similarity or lack of likeness in appearance to something else. 

selfsameness

noun
  • The property of two or more appearances of being of the selfsame underlying object; sameness as regards self or identity; identity; identicality. 

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