assignee vs successor

assignee

noun
  • one to whom a thing is assigned 

  • one to whom rights or property is being transferred 

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

successor

noun
  • A person who inherits a title or office. 

  • The next heir in order or succession. 

  • A person or thing that immediately follows another in holding an office or title. 

  • The integer, ordinal number or cardinal number immediately following another. 

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