I’ve always heard it in rap songs, and from people I know who think it’s funny. Another in the same catagory would be “One time”.
Well, that explains it: as an old, East Coast white woman, I always called them “coppers.”
So how does it fit into Kevin Federline’s “Po-po Zao” that they mecilessly poke fun of on The Soup?
Sis? Is that you???
(I’m freaked. I thought it was just my mom being weird.)
Heard as slang for the police in Oregon as early as 1982.
Count me in as another who heard “pat em on the po po” as a child. However while po po did refer to one’s backside my mother never used it as part of a diaper changing song. “Pat em on the po po” was my mother’s term for a smack on the butt for misbehaving. “Knock it off or you all are going to get a pat on the po po!!”
Much like Ginger of the North I didn’t hear the term again until I became familiar with the habits of stoop kids and corner kids in West Baltimore. There it is used exclusively to mean police.
Now, that has something to do with >ahem< patooties. And umlauts.
As a toddler, this was the term our family used to refer to that part of the body technically known as the “wee wee.”
I grew up in Virginia and am familiar with the term. I have also heard it used as a singular noun.
FWIW, I have never heard it used in a derogatory sense.
Technically, it could be both a butt and a hoo-hoo. At our house.
I didn’t know what a vagina was til I was 37.
“Feet up! Pat 'em on the po-po! Let’s hear him laugh?”
It was a fairly popular novelty song in 1952.
Here’s a sound file of it.
“Cooter” down here in the South.
Just lettin’ y’all know and trying to be helpful! 
Q
Californian weighing in here: I never heard the expression in Monterey, Marina, San Francisco, San Jose, Mountain View, Oakland, or Alameda.
Aren’t straight lines supposed to be reserved for MPSIMS or the Pit?
Hey, I’m just glad that so far no one has pointed out that meth is a drug.
Another Californian weighing in with ‘I have never heard the term before seeing it in the Pit thread’.
I’m a native Texan and I heard it here in the mid or late-90’s. Before then, I was probably too young anyway.
It sounds almost like another term for someone’s grandfather-similiar to “Pappap”.
I first heard it used on NYPD Blue, as Andy Sipowicz asks his young son if somebody touched him on the po-po.
When I first saw the thread title, my first thought was “one old lady shot another old lady?”
Popo is Chinese for “maternal grandmother” (Cantonese, I think).