anilingus vs butt-fucking

anilingus

noun

  • A form of oral sex in which the tongue and lips are used for stimulation of a sexual partner's anus. 

butt-fucking

noun

  • anal sex 

adj

  • Engaging in anal sex 

How often have the words anilingus and butt-fucking occurred in a corpus of books? (source: Google Ngram Viewer )