sever vs unify

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. 

unify

verb
  • Cause to become one; make into a unit; consolidate; merge; combine. 

  • Become one. 

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