irritate vs pester

irritate

verb
  • To provoke impatience, anger, or displeasure in. 

  • To cause or induce displeasure or irritation. 

  • To induce pain in (all or part of a body or organism). 

pester

verb
  • To bother, harass, or annoy persistently. 

noun
  • A bother or nuisance. 

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