adultery vs troilism

adultery

noun
  • Sexual intercourse by a married person with someone other than their spouse. 

  • Lewdness or unchastity of thought as well as act, as forbidden by the seventh commandment. 

  • Faithlessness in religion. 

  • The intrusion of a person into a bishopric during the life of the bishop. 

  • Adulteration; corruption. 

troilism

noun
  • The practice of two people having sex while a third person watches (and may or may not take part). 

  • The practice of three people having sex, i.e. having threesomes. 

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