anus vs rectum

anus

noun
  • The lower orifice of the alimentary canal, through which feces and flatus are ejected. 

  • An impolite, unpopular, or unintelligent person. 

rectum

noun
  • The terminal part of the large intestine through which feces pass after exiting the colon, but before leaving the body through the anus. 

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