purser vs treasurer

purser

noun
  • The person responsible for handling the accounts on a ship, or for dealing with the passengers on a ship or aircraft. 

treasurer

noun
  • The official entrusted with the funds and revenues of an organization such as a club. 

  • The government official in charge of the Treasury. 

  • The head of a corporation's treasury department. 

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