disjoin vs sever

disjoin

verb
  • To separate; to disunite. 

  • To become separated. 

sever

verb
  • To suffer disjunction; to be parted or separated. 

  • To disconnect; to disunite; to terminate. 

  • To make a separation or distinction; to distinguish. 

  • To cut free. 

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