assignee vs heir

assignee

noun
  • one to whom rights or property is being transferred 

  • one to whom a thing is assigned 

  • one who is appointed to act or speak in place of another; an agent 

heir

noun
  • Someone who inherits, or is designated to inherit, the property of another. 

  • A successor in a role, representing continuity with the predecessor. 

  • One who inherits, or has been designated to inherit, a hereditary title or office. 

verb
  • To inherit. 

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