gaffer vs line manager

gaffer

noun
  • The leader of a group or team, such as a boss, foreman, coach, publican. 

  • A chief lighting technician for a motion-picture or television production. 

  • The baby in the house. 

  • A sailor. 

  • An old man. 

  • A glassblower. 

line manager

noun
  • The manager who is directly responsible for an employee. 

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