gravamen vs name of the game

gravamen

noun
  • The essence or most important aspect of a piece of writing, a point of argument, etc.; the gist. 

  • A grievance complained of. 

  • The essence or ground of a complaint. 

  • A document sent by the Lower House of Convocation to the Upper House to inform the latter of certain grievances in the church. 

name of the game

noun
  • The essential element (needed to reach the principal goal or objective); the overall purpose. 

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