pair off vs sever

pair off

verb
  • To join two people into a relationship. 

  • To separate into groups of two. 

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. 

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