impede vs shut down

impede

verb
  • To get in the way of; to hinder. 

shut down

verb
  • To turn off or stop. 

  • To pass (another vehicle), especially quickly. 

  • To close, terminate, or end. 

  • To emotionally withdraw into oneself as a defense mechanism; to block out external stressors. 

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