concordat vs indenture

concordat

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

indenture

noun
  • A document, written as duplicates separated by indentations, specifying such a contract. 

  • A contract which binds a person to work for another, under specified conditions, for a specified time (often as an apprentice). 

  • An indentation; a recess. 

verb
  • To indent; to make hollows, notches, or wrinkles in; to furrow. 

  • To bind a person under such a contract. 

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