purser vs servitor

purser

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

servitor

noun
  • One who performs the duties of a servant. 

  • One who serves in an army; a soldier. 

  • An undergraduate who performed menial duties in exchange for financial support from his college, particularly at Oxford University. 

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