convulse vs tremble

convulse

verb
  • To violently shake or agitate. 

  • To suffer violent involuntary contraction of the muscles, producing contortions of the body or limbs. 

  • To create great laughter. 

tremble

verb
  • To shake, quiver, or vibrate. 

  • To fear; to be afraid. 

noun
  • A shake, quiver, or vibration. 

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