tremble vs tremor

tremble

noun
  • A shake, quiver, or vibration. 

verb
  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

tremor

noun
  • A shake, quiver, or vibration. 

  • An earthquake. 

  • A rhythmic, uncontrollable shaking of all or part of the body due to partial muscle contractions. 

verb
  • To shake or quiver excessively and rapidly or involuntarily; to tremble. 

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