operant vs spook

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. 

spook

noun
  • An undercover agent or spy. 

  • A ghost or phantom. 

  • A hobgoblin. 

  • A scare or fright. 

  • A psychiatrist. 

  • A player who engages in hole carding by attempting to glimpse the dealer's hole card when the dealer checks under an ace or a 10 to see if a blackjack is present. 

  • A metaphysical manifestation; an artificial distinction or construct. 

verb
  • To frighten or make nervous (especially by startling). 

  • To become frightened (by something startling). 

  • To haunt. 

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