retraction vs say so

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. 

say so

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