compulsory purchase vs eminent domain

compulsory purchase

noun
  • The power of a state to expropriate private land within its jurisdiction for public use. 

eminent domain

noun
  • The right of a government over the private property within its jurisdiction. Usually invoked to compel land owners to sell their property in preparation for a major construction project such as a freeway. 

  • In feudalism, the legal interest or rights of a lord or superior in an estate in land held in fee, as opposed to the vassal's or tenant's interest. 

How often have the words compulsory purchase and eminent domain occurred in a corpus of books? (source: Google Ngram Viewer )