piss one's pants vs trousers

piss one's pants

verb
  • To be extremely frightened. 

  • To laugh uncontrollably. 

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

trousers

noun
  • An article of clothing that covers the part of the body between the waist and the ankles or knees, and is divided into a separate part for each leg. 

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