sever vs unrestrict

sever

verb
  • To cut free. 

  • To disconnect; to disunite; to terminate. 

  • To make a separation or distinction; to distinguish. 

  • To suffer disjunction; to be parted or separated. 

unrestrict

verb
  • To free from restrictions. 

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