placation vs weakening

placation

noun
  • A process or act of placating; appeasement or an expression of appeasement. 

weakening

noun
  • An instance or process of loss of strength. 

  • A structural principle of mathematical logic that states that the hypotheses of any derived fact may be freely extended with additional assumptions. 

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