charley horse vs convulsion

charley horse

noun
  • A muscle cramp, usually in the thigh or leg. 

convulsion

noun
  • An intense, paroxysmal, involuntary muscular contraction. 

  • An uncontrolled fit, as of laughter; a paroxysm. 

  • Violent turmoil. 

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