sever vs split up

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. 

split up

verb
  • separate, disassociate, cause to come apart. 

  • Cease to be together, break apart from the group. 

adj
  • Divided or separated. 

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