spook vs tremble

spook

verb
  • To become frightened (by something startling). 

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

  • To haunt. 

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. 

tremble

verb
  • To fear; to be afraid. 

  • To shake, quiver, or vibrate. 

noun
  • A shake, quiver, or vibration. 

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