The term is thought to have originated with the pornographic magazine "Razzle". Razzle had a recurring theme of showing ladies stacked on top of each other either in doggystyle or missionary position with their vaginas displayed. Such an extravagant display of vaginas is called a Razzlestack.
"The gynaecologist had a razzlestack of vaginas to work through this morning".
"The young man looked around the razzlestack in the student union bar with a sense of nostalgia and regret".
"The bar had a whole razzlestack of cunts in tonight".