corroboration vs retraction

corroboration

noun
  • That which corroborates. 

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

retraction

noun
  • A continuous function from a topological space onto a subspace which is the identity on that subspace. 

  • An act or instance of retracting. 

  • A statement printed or broadcast in a public forum which effects the withdrawal of an earlier assertion, and which concedes that the earlier assertion was in error. 

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