operant vs procurator

operant

noun
  • An operative person or thing. 

  • Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment. 

adj
  • That operates to produce an effect. 

procurator

noun
  • An agent or attorney. 

  • A tax collector. 

  • The governor of a small imperial province. 

  • A legal officer who both investigates and prosecutes crimes, found in some inquisitorial legal systems, particularly communist or formerly communist states – see public procurator 

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