cooter vs tunnel of love

cooter

noun
  • Vagina or vulva. 

  • The box turtle. 

  • A redneck. 

  • A freshwater turtle of the eastern United States of the genus Pseudemys. 

tunnel of love

noun
  • The vagina. 

  • A carnival dark ride for couples in boats, either relaxing and romantic, or spooky (encouraging the couple to cling to one another). 

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