emissary vs errand boy

emissary

noun
  • An agent sent on a mission to represent the interests of someone else. 

  • An underground channel by which the water of a lake escapes. 

  • A venous channel in the skull. 

errand boy

noun
  • Someone in a responsible position who performs relatively menial tasks for a senior manager. 

  • A male employed to run errands. 

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