immunity vs obligatoriness

immunity

noun
  • An exemption from specified duties, such as payments or services. 

  • An exemption from penance. 

  • An exemption given to a player from losing or being withdrawn from play. 

  • A resistance to a specific thing. 

  • An exemption from prosecution. 

  • Protective resistance against disease. 

obligatoriness

noun
  • The quality or state of being obligatory. 

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