chairman vs political commissar

chairman

noun
  • A person presiding over a meeting. 

  • The head of a corporate or governmental board of directors, a committee, or other formal entity. 

  • Someone whose job is to carry people in a portable chair, sedan chair, or similar conveyance. 

verb
  • To serve as chairman. 

political commissar

noun
  • A supervisory political officer responsible for ideological education and organization. 

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