bona fides vs insincerity

bona fides

noun
  • Credentials that authenticate a person's good standing or reputation. 

  • Sincerity, good faith. 

insincerity

noun
  • Property of being insincere, lacking sincerity or truthfulness. 

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