The great, gravel voiced English singer Bernard Wrigley has a marvelous song called "Plastic Pies." The chorus has an indelicated phrase I've never fully understood:

...and you can shove 'em where the monkey shoves his nuts!

I get the general anatomical idea -- akin to "where the sun never shines." But does anyone know if this is a reference to actual monkey behavior. And (please forgive my earnest ignorance), does the saying refer to what monkeys do with their food or their testicles?

(By the way, I noticed almost the same phrase in the Fairport Convention song "Big William" posted on DigiTrad when I was looking for something else just now.)

Thanks, as always, for any information. Yours, from the great borough of Brooklyn, New York.