bird dog vs spook

bird dog

verb
  • To seek out. 

  • A multiservice tactical brevity code requesting configuration of sensors. 

  • To watch closely. 

noun
  • A dog, especially a pointer, used in shooting to retrieve the dead birds. 

  • A tout. 

  • A person who seeks out real estate investment opportunities in exchange for a fee. 

  • A person who tries to steal someone else's romantic partner 

  • A radar detector (for detecting police speed traps). 

  • A hyperextension exercise performed lying on the knees, with one arm and the opposite leg lifted. 

spook

verb
  • To haunt. 

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

  • To become frightened (by something startling). 

noun
  • A ghost or phantom. 

  • An undercover agent or spy. 

  • 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. 

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