pick at vs worry

pick at

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

  • To pick on or repeatedly criticize (someone). 

worry

verb
  • To touch repeatedly, to fiddle with. 

  • To harass; to irritate or distress. 

  • To be troubled; to give way to mental anxiety or doubt. 

  • To seize or shake by the throat, especially of a dog or wolf. 

  • Disturb the peace of mind of; afflict with mental agitation or distress. 

noun
  • A strong feeling of anxiety. 

  • An instance or cause of such a feeling. 

  • A person who causes worry. 

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