chief executive vs senior captain

chief executive

noun
  • Chief executive officer. 

  • The president of the United States. 

  • The head of government of Hong Kong 

  • The head of government of Macau 

  • The governor of a U.S. state. 

senior captain

noun
  • a military rank for a field officer above that of captain and below that of major 

  • a military rank for a naval officer above that of captain and below the admiral ranks or flag ranks 

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