somnific vs stupefacient

somnific

adj

  • Causing sleep; somniferous. 

stupefacient

adj

  • Inducing stupor or drowsiness (with a drug such as a narcotic or an anaesthetic). 

noun

  • Any drug that induces stupor or drowsiness. 

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