concede vs pick at

concede

verb
  • To admit or agree to be true; to acknowledge. 

  • To yield or suffer; to surrender; to grant 

  • To yield or make concession. 

  • (of a bowler) to have runs scored off of one's bowling. 

  • To grant, as a right or privilege; to make concession of. 

  • To have a goal or point scored against 

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 concede and pick at occurred in a corpus of books? (source: Google Ngram Viewer )