referee vs reviewer

referee

noun
  • An expert who judges the manuscript of an article or book to decide if it should be published. 

  • A person who settles a dispute. 

  • An umpire or judge; an official who makes sure the rules are followed during a game. 

  • A person who writes a letter of reference or provides a reference by phone call for someone. US English: reference. 

verb
  • To act as a referee. 

reviewer

noun
  • A person who writes reviews for a newspaper or other publication; a critic. 

  • An inspector. 

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