acerbity vs severity

acerbity

noun
  • Something harsh (e.g. a remark, act or experience). 

  • Harshness, bitterness, or severity 

  • Sourness of taste, with bitterness and astringency, like that of unripe fruit. 

severity

noun
  • The degree of something undesirable; badness or seriousness. 

  • The state of being severe. 

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