assent vs corroboration

assent

noun
  • agreement; act of agreeing 

verb
  • To agree to a proposal. 

corroboration

noun
  • The act of corroborating, strengthening, or confirming; addition of strength; confirmation 

  • That which corroborates. 

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