The other day I went with a friend to Patronato, the cheap imported and locally-made clothing neighborhood here in Santiago where everything fits you perfectly if you are a size four to six, which is curious since almost nobody is in Chile. At any rate, my friend had a mission to buy some prendas (garments) there in Patronato and I went with her and checked out a couple of prendas myself, most of which had a low-cuttiness (and the rhyme you're currently thinking of) to them that I simply could not abide. I'm not a very conservative dresser, but I spend a lot of time deflecting piropos already, and I just don't see any reason to add fuel to the fire.
We marveled at the body type of the mannequins they used to model the pants, and the potos parados (bubble butts) that they had, considering that that is also not the body type of most Chilenas. We also looked at each other quizically over racks and racks of one-size-fits-who saggy-butted pants, made of beautiful Indian fabrics, but which kind of make people look like they're wearing diapers. Bombachas (bloomers) in local parlance, if you were wondering.
Not that long ago, I had seen a woman wearing a shirt with the words you see above: Shake that bums girls. It confused me, because it's gramatically wrong. Should be shake those bums girls. Or shake that bum girls.
Or should it? I reparsed the sentence and came up with this: What if it's a shake (as in a drink) that's really delicious, but really bad for you? That would make women sad. Shake that bums girls. Get it? So in my mind I had it as a strange but attention-grabbing marketing scheme for some kind of drink. The green tea frappucino from Starbucks, perhaps?
No matter how you parse it, I have found the source. Patronato. Which really isn't that surprising, given some of the other shirt-os I've seen around Chile. It's no Engrish but it makes me smile anyway.