bitter pill vs bummer

bitter pill

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

bummer

noun
  • A disappointment, a pity, a shame. 

  • A lamb (typically the smallest of a multiple birth) which has been abandoned by its mother or orphaned, and as a consequence is raised in part or in whole by humans. 

  • A gay man. 

intj
  • Exclamation of annoyance or frustration at a bummer (disappointment). 

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