copulation vs sex drive

copulation

noun
  • Sexual procreation between a man and a woman or transfer of the sperm from male to female; usually applied to the mating process in nonhuman animals; coitus; coition. 

  • The act of coupling or joining; union; conjunction. 

sex drive

noun
  • The tendency or instinct of animals to engage in sexual activity. 

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