bitter pill vs scourge

bitter pill

noun
  • Used other than figuratively or idiomatically: see bitter, pill. 

scourge

noun
  • A means to inflict such pain or destruction. 

  • A source of persistent trouble such as pestilence that causes pain and suffering or widespread destruction. 

  • A whip, often of leather and often multi-tailed. 

verb
  • To strike with a scourge; to flog. 

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