chairman vs chief executive officer

chairman

noun
  • 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. 

  • A person presiding over a meeting. 

verb
  • To serve as chairman. 

chief executive officer

noun
  • The highest-ranking corporate officer or executive officer of a corporation, company, or agency, responsible for carrying out the policies of the board of directors on a day-to-day basis; CEO. 

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