restrain vs unshackle

restrain

verb
  • To control or keep in check. 

  • To deprive of liberty. 

  • To strain again. 

  • To restrict or limit. 

unshackle

verb
  • To remove restrictions or inhibitions; to allow full freedom and power. 

  • To remove shackles from someone or something. 

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