exasperate vs pester

exasperate

verb
  • To tax the patience of; irk, frustrate, vex, provoke, annoy; to make angry. 

pester

verb
  • To bother, harass, or annoy persistently. 

noun
  • A bother or nuisance. 

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