sever vs unsnib

sever

verb
  • To disconnect; to disunite; to terminate. 

  • To make a separation or distinction; to distinguish. 

  • To cut free. 

  • To suffer disjunction; to be parted or separated. 

unsnib

verb
  • to undo, untie, or open or become undone, untied, or opened. 

  • Somehow she managed to unsnib the window and escape. 

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