palliative vs tranquilizer

palliative

noun
  • Something that palliates, particularly a palliative medicine. 

adj
  • Serving to palliate; serving to extenuate or mitigate. 

  • Minimising the progression of a disease and relieving undesirable symptoms for as long as possible, rather than attempting to cure the (usually incurable) disease. 

tranquilizer

noun
  • That which tranquillizes or soothes. 

  • A drug used to reduce anxiety or tension. 

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