pester vs vex

pester

verb
  • To bother, harass, or annoy persistently. 

noun
  • A bother or nuisance. 

vex

verb
  • To annoy, irritate. 

  • To toss back and forth; to agitate; to disquiet. 

  • To twist, to weave. 

  • To cause (mental) suffering to; to distress. 

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