severance vs unification

severance

noun
  • A separation. 

  • The act of severing or the state of being severed. 

  • A severance payment. 

unification

noun
  • Given two terms, their join with respect to a specialisation order. 

  • The act of unifying. 

  • The state of being unified. 

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