heroin vs tranquilizer

heroin

noun
  • A powerful and addictive drug derived from opium producing intense euphoria. Classed as an illegal narcotic in most of the world. 

tranquilizer

noun
  • A drug used to reduce anxiety or tension. 

  • That which tranquillizes or soothes. 

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