piss one's pants vs shart

piss one's pants

verb
  • To wet oneself; to urinate in one's own clothes while they are being worn. 

  • To be extremely frightened. 

  • To laugh uncontrollably. 

shart

verb
  • To unintentionally defecate due to relaxing the anus to flatulate. 

noun
  • An instance of sharting. 

  • The resulting excrement from sharting. 

How often have the words piss one's pants and shart occurred in a corpus of books? (source: Google Ngram Viewer )