chauffeur vs copilot

chauffeur

noun
  • A person employed to drive a private motor car or a hired car of executive or luxury class (like a limousine). 

  • The driver of a fire truck. 

verb
  • To be, or act as, a chauffeur (driver of a motor car). 

  • To transport (someone) in a motor vehicle. 

copilot

noun
  • A backup or assistant pilot of an aircraft. 

verb
  • To serve as relief or assistant pilot. 

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