Someone happened to use the phrase "the 59th minute of the eleventh hour" just now on IRC (#lisp on Freenode). I remarked that that should be "the twelfth hour". This then started me wondering where that apparently nonsensical phrase came from. It means at the last minute, of course, but in what sense is the eleventh hour the last minute? A quick google finds, for example http://en.wiktionary.org/wiki/eleventh_hour, but that doesn't really explain anything. The Biblical usage seems to mean "late in the day" (apparently 5 pm or so), not "at the last minute". Or is it just that the meaning of the phrase has changed slightly over time?
Learn English – the origin of the phrase “the eleventh hour”
etymology
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Ungodly is being used in the sense of outrageous; shocking; dreadful; insufferable, rather than invoking any of its religious meanings. So "an ungodly hour" just means "an outrageous time of day".
But how did the phrase come to have a connotation of earliness?
When people complain about an "ungodly hour", it is usually because they are forced to be awake when they would prefer to be asleep.
It's not unusual to be compelled to get up earlier than you wish. Some people must get up early every weekday just to get to work on time. And on occasion they might have to get up very early - to catch an early flight, for example.
It is far less common to be required to stay up late.
So, in most people's experience, when they find themselves talking about an "ungodly hour", it is far more likely to be an early one than a late one.
The answer to your question is "Gare à l'eau!" or less commonly nowadays "Gare l'eau!" [=look out for the water!].
Actually I have never heard anyone say "gare quelque chose." The typical phrasing is "gare à quelque chose" [look out/watch out for something] in modern day French.
E.g.
"Gare à la voiture!" or even more commonly "Attention à la voiture!" [Watch out for the car!]"
That said, "Gare la voiture!" is grammatically correct and standard French, but is more likely to be found in literary works.
Besides, interjective "gare à" when addressed to someone is an invective exclamation. E.g. Gare a toi! [Watch out!]; Gare à ce que tu dis! [Mind/watch what you're saying!].
In conclusion, Farlex Trivia Dictionary knows best.
Wiktionary "Garde à l'eau (or more commonly dans l'eau) lit. "guard in the water," the typical French expression being "homme à la mer," lit. "man in the sea" [man overboard]) = Guard overboard, but "Garde! A l'eau!" = Guard! (Get yourself) into the water! Plus, "Garde! A l'eau!" can also be understood as "Guard! Come get your water/Water's served," the typical French expression being "A la soupe!" [Soup's ready/served!].
The Free Dictionary "Gare de l'eau" = The Water Station, but "Gare! De l'eau!" = Watch out! Water's coming!
oxforddictionaries "Regarde l'eau" = Look at the water!
unusuedwords.com "Garde de l'eau" = Spare some water (=don't use it all), or "Garde l'eau" = (You can) keep the water.
NB: In everyday speech, if you say to a French person "Gare la voiture" in a monotonous tone, chances are it'll be understood as "park the car," as long as there's also a verb, "garer" [to park], which is declined into "gare" in the present simple, the present subjunctive, and the imperative.
Edit: What actually is quoted in the Free Dictionary is not "gare à l'eau" [look out for the water], but "gare de l'eau," which still makes lots of sense in French provided the appropriate punctuation is added: "Gare de l'eau" [=The Water Station], but "Gare! De l'eau!" [Watch out/look out! Water's coming!]. Hence the most logic English transcription "Gardyloo!".
Best Answer
Its origin is biblical and refers to the parable of the labourers in the vineyard (Matthew XX)
The OED gives some indication of the etymology of the modern expression from as early as 971AD.