nark vs roper

nark

noun
  • A police spy or informer. 

  • An unpleasant person, especially one who makes things difficult for others. 

verb
  • To stop. 

  • To annoy or irritate. 

  • To serve or behave as a spy or informer. 

  • To complain. 

  • To watch; to observe. 

roper

noun
  • An undercover informer. 

  • One who ropes goods; a packer. 

  • Synonym of outside man (“accomplice who locates a mark to be swindled by a confidence trickster”) 

  • Any of a variety of monsters with tentacles that they use to capture victims. 

  • A person hired by a gambling establishment to locate potential customers and bring them in. 

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