dissimilitude vs heterogeneity

dissimilitude

noun
  • The quality of being diverse or different; lack of resemblance. 

heterogeneity

noun
  • Diversity 

  • A composition of diverse parts. 

  • The quality of a substance which is not uniform. 

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