case officer vs handler

case officer

noun
  • A person assigned to manage a client's affairs. 

  • In intelligence organisations, a person who manages a network of agents. 

handler

noun
  • One who handles something (especially manually) or someone. 

  • An advisor or manager to a person occupying a position or office to which the speaker believes the holder does not possess the typical qualifications and/or experience. 

  • A subroutine that handles a particular situation such as an event or exception. 

  • A controller, trainer, someone who handles a specified thing, animal or person (especially a prizefighter). 

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