keister vs posterior

keister

noun
  • The anus or buttocks. 

  • A suitcase or satchel. 

verb
  • To conceal something in one's rectum 

posterior

noun
  • The hinder parts of the body. 

  • The probability that a hypothesis is true (calculated by Bayes' theorem). 

adj
  • Following in order or in time. 

  • Next to, or facing the main stem or axis. 

  • Relating to or denoting presentation of a fetus in which the rear or caudal end is nearest the cervix and emerges first at birth. 

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