black tar vs laudanum

black tar

noun
  • An illicit drug formed from the incomplete acetylation of morphine, containing a variable percentage of heroin. 

laudanum

noun
  • A tincture of opium, once widely used for various medical purposes and as a recreational drug. 

verb
  • To cause (a person) to be high on laudanum. 

  • To add laudanum to (a drink or the like). 

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