amalgamation vs pledging

amalgamation

noun

  • The production of an alloy of mercury and another metal. 

  • The result of amalgamating; a mixture or alloy. 

  • The process of amalgamating; a mixture, merger or consolidation. 

pledging

noun

  • The making of a pledge. 

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