coupling vs notch on one's bedpost

coupling

noun
  • Sexual intercourse. 

  • The property of physical systems that they are interacting with each other 

  • Act of joining together to form a couple. 

  • A device that couples two things together. 

  • The degree of reliance between two or more software modules. 

  • A connection between two electronic circuits such that a signal can pass between them. 

notch on one's bedpost

noun
  • A sexual conquest; a casual sexual partner. 

How often have the words coupling and notch on one's bedpost occurred in a corpus of books? (source: Google Ngram Viewer )