I'm reliably informed by the Fiance that this particular part of the anatomy is called a "Tuppence"
Strangly however the dogs "Tuppence" is called a "Foof".
My close knit circle of chums jokingly refer to it as:
The hairy axe wound
The bearded clam
Snatch/Gash
Bikini Burger
and Sausage Canyon. Yes, yes, we're classy folk.