fluctuation vs tremor

fluctuation

noun
  • A wavering; unsteadiness. 

  • In medicine, a wave-like motion or undulation of a fluid in a natural or abnormal cavity (e.g. pus in an abscess), which is felt during palpation or percussion. 

  • A motion like that of waves; a moving in this and that direction. 

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 fluctuation and tremor occurred in a corpus of books? (source: Google Ngram Viewer )