have a fit vs shit oneself

have a fit

verb
  • To become suddenly enraged. 

  • To experience an epileptic seizure. 

shit oneself

verb
  • To be very frightened or astonished (to the extent that one might lose control of one's bowels). 

  • To soil oneself. 

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