doggy style vs retrocopulation

doggy style

noun

  • The position assumed for doggy style intercourse. 

adv

  • In a position whereby one partner is on all fours and the other partner is penetrating from behind. 

adj

  • With one partner on all fours and the other penetrating from behind. 

retrocopulation

noun

  • Copulation from behind. 

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