Back in my Theatre Major days in college (and yes, we did spell it poncy like that despite being in ‘Merica), they taught us an important shout. That shout was “heads!”
What did that mean? Basically to get the hell out of the way because someone up in the rigging just dropped something heavy. It was most likely short for “heads up!” but shortened to one syllable since every second counts in a situation like that. Also you probably shouldn’t actually be looking up in response since the only good that would do would be letting you see the wrench about to land on your face.
There was the possibility of course that you might dodge *into* the danger by accident, but at least you were aware of it. Plenty of warning words and phrases like this are sprinkled throughout the English language, e.g. “look out!” or “duck!” or even that mainstay of golf, “fore!”
Then I thought of the Flores family, who are obviously bilingual but one of the phenomena that can happen there is that in times of stress you might revert back to your native language. How would you shout “look out!” in Spanish, particularly Mexican Spanish (since when you get into slang it can diverge as much as Australia and America).
A little research and consultation and I had an intriguing answer, which was ¡Aguas!
But wait, you may ask, doesn’t that just mean “water?”
Yes, but it’s all about the context isn’t it? Just like “duck” is a species of waterfowl unless you happen to be shouting it at someone with concern in your tone. Duck is apparently from an Old English word meaning to submerge or dive and was applied to the way that certain common waterfowl will often upend itself seeking something to eat. It also explains the name of the unpleasant practice known as ducking a witch.
In the case of aguas, the derivation of the warning usage turns out to be more in line with “heads!” as it is generally surmised to be a term coming from before indoor plumbing when the common practice was to toss your dirty bathwater (and worse) out into the street, sometimes from an upper window. Not a practice unique to Spain or Mexico, just crowded cities in general, but here it was basically saying there was some nasty liquid about to rain down and you might be well advised to run for cover. And rather than wasting time specifying the particular kind of nasty liquid it was shortened down but everyone knew (or would quickly learn) that it was not going to be the kind of water you’d get fresh from mountain springs.
Fast forward to where indoor plumbing has become commonplace in most cities around the globe including the Spanish-speaking ones, but much like “half cocked” the slang has survived and in modern usage has little to do with literal water or liquid but just a way to quickly and loudly let someone know to be wary. Pay attention. “Duck” and cover.
I’m sure at least as many puns have been made based on that as we’ve done with “duck” but where actual danger is involved it’s probably best to dodge first and think about the particulars later.