isolate vs sever

isolate

verb
  • To set apart or cut off from others. 

  • To self-isolate. 

  • To separate a pure strain of bacteria etc. from a mixed culture. 

  • To separate a substance in pure form from a mixture. 

  • To insulate, or make free of external influence. 

  • To insulate an electrical component from a source of electricity. 

  • To place in quarantine or isolation. 

noun
  • Something that has been isolated. 

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 isolate and sever occurred in a corpus of books? (source: Google Ngram Viewer )