go-between vs souteneur

go-between

noun
  • An intermediary or middleman. 

  • A shogi piece, used in chu shogi and larger shogi variants, that can move one step straight forward or straight backwards. 

souteneur

noun
  • A man who protects a prostitute and lives off her earnings; a pimp. 

How often have the words go-between and souteneur occurred in a corpus of books? (source: Google Ngram Viewer )