indenture vs mastery

indenture

noun
  • 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. 

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

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

  • To bind a person under such a contract. 

mastery

noun
  • The position or authority of a master; dominion; command; supremacy; superiority. 

  • Superiority in war or competition; victory; triumph; preeminence. 

  • The act or process of mastering; the state of having mastered; expertise. 

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