enfetter vs pin down

enfetter

verb
  • To bind in fetters; to enchain. 

pin down

verb
  • To attach or secure with pins. 

  • To hold the opponent back-first so both his or her shoulders touch the mat or ground. 

  • To identify something (e.g. a decision or plan) clearly or specifically. 

  • To corner somebody in order to get a firm answer. 

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