painkiller vs palliative

painkiller

noun
  • A drug that numbs the pain in the body. 

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. 

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