convulse vs dry-heave

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. 

dry-heave

verb
  • To attempt to vomit with the ejection of only gas. 

noun
  • An attempt to vomit that ejects only gas. 

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