acerbate vs mither

acerbate

verb
  • To exasperate; to irritate. 

  • To make bitter or sour. 

adj
  • Embittered; having a sour disposition or nature. 

mither

verb
  • To pester or irritate someone. 

  • To make an unnecessary fuss, moan, bother. 

noun
  • mother 

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