unbar vs unchain

unbar

verb
  • To remove a prohibition. 

  • To remove an impediment that obstructs the passage of (someone or something). 

  • To unlock or unbolt a door that had been locked or bolted with a bar. 

unchain

verb
  • To remove chains from; to free; to liberate. 

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