concordat vs treaty

concordat

noun
  • A formal agreement between two parties, especially between a church and a state; specifically, an agreement between the Pope and a government. 

treaty

noun
  • A formal binding agreement concluded by subjects of international law, namely, states and international organizations; a convention, a pact. 

verb
  • To get into (a specific situation) through a treaty. 

  • To enter into a treaty. 

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