pester vs pick at

pester

verb
  • To bother, harass, or annoy persistently. 

noun
  • A bother or nuisance. 

pick at

verb
  • To pick on or repeatedly criticize (someone). 

  • To touch, grab, handle, or pull tentatively or gingerly, using a utensil or one's fingers. 

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