"Secret
Diplomatic Negotiations" is a comical euphemism for anal sex. It was coined over at www.apennyforlenny.com, based on a Jeopardy clue.
The clue was from the category "BACK" TO SCHOOL. It was:
“SECRET DIPLOMATIC
NEGOTIATIONS ARE SAID TO GO THROUGH THIS”
The answer was "WHAT IS THE BACKDOOR?"
"Could I interest any of you ladies in some Secret Diplomatic
Negotiations?"
"Yeah, me and Becky Diplomatically Negotiated in Secret all night long."
"If you're ever in prison, watch out for the Secret Diplomatic
Negotiations that happen
in the shower."