casuistry vs duplicity

casuistry

noun
  • A specious argument designed to defend an action or feeling. 

  • The process of answering practical questions via interpretation of rules, or of cases that illustrate such rules, especially in ethics; case-based reasoning. 

duplicity

noun
  • Intentional deceptiveness; double-dealing. 

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