prostitution vs the oldest profession

prostitution

noun
  • Engaging in sexual activity with another person in exchange for goods (not necessarily money) or services. 

  • Debasement for profit or impure motives. 

  • Engaging in sexual activity with another person for pay. 

the oldest profession

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