armed robbery vs rip-off

armed robbery

noun
  • An theft where the thieves are carrying weapons. 

rip-off

noun
  • A theft or robbery. 

  • A copy, especially one that is illegal or inferior. 

  • A bad deal; an unfair or exorbitant price or rate. 

  • A scam. 

How often have the words armed robbery and rip-off occurred in a corpus of books? (source: Google Ngram Viewer )