Captain vs commissioner

Captain

noun
  • An army officer title in most countries 

  • The title for someone who holds the captain job on a ship or other vessel. 

commissioner

noun
  • An official in charge of a government department, especially a police force. 

  • Someone commissioned to perform certain duties. 

  • A member of a commission. 

  • Someone who commissions something. 

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