bowel movement vs purging

bowel movement

noun
  • The discharge of feces from the body, an act of defecation. 

  • The feces thus produced. 

purging

noun
  • The removal of digested waste: defecation; defecation induced by laxatives. 

  • Vomiting; vomiting induced by purgatives. 

  • A removal of undesirable people. 

  • The cleansing of a device by flushing it with water, steam, or some other liquid or gas. 

  • The removal of excess humors through bloodletting, induced vomitting, etc. 

How often have the words bowel movement and purging occurred in a corpus of books? (source: Google Ngram Viewer )