Before we get to the heart of the matter, let's look at a few words. Like trasero.
Trasero basically means "rear end". And yes, I'm talking about the old gluteus maximus. There's also pompis, which is more like bottom. And then we have culo, which is pretty much the equivalent of "ass". This is considered pretty rude in Mexican Spanish, so beware!
So if we wanted to use these words to say how attractive we find someones rear end, we could say:
Tienes buen trasero
Tienes buenas pompis
Tienes buen culo
These work for either sex, so feel free to tell your special someone, man or woman, about their buns of steel. Just remember that in Mexican Spanish culo is rude, so be sure you're using it at the right time with the right audience.
Now we can get to our phrase, which uses the last word we need to discuss, nalgas.
Nalgas translates to butt-cheeks. So you can add "Tienes buen nalgas", to your list of compliments.
And now we finally get to "Nálgame dios".
Guys, the next time you find yourself walking down the street with your buddies, and a hottie with a nice "backyard" comes into view, feel free to let out a "¡Nálgame dios!" . It's considered pretty rude, so be careful.
Ladies, sorry, but I don't know if this is something women say or not. But at least you'll know what it means if someone directs this at you, and you can respond accordingly, whether it be a friendly wink of the eye or a cachetada (slap in the face).
Let's talk about a couple of related words...
A nalgona is a woman with "junk in the trunk", a large, shapely bottom. And a nalgada is a slap on the bottom. You may also hear someone say "pegame" if they're asking for a spanking.
That's it for today!
¡Hasta la próxima!