What is the meaning of this?

[gleaming sail]

"Du hast in deines Ärmels falten" like is this an expression for something

This is more than 200 years old text so the translation would not necessarily match a modern concept of the statment.

[patent reef]

Is this the complete context? Because the most likely explanation I would think of would be "Du hast in deines Ärmels Falten [some object here]", which would mean "In the folds of your sleeve you have [some object here]", if "falten" would indeed be written without a capital letter, it might refer to the verb instead of the noun (which is also translated to English as "to fold"), but which would not make immediate sense to me. Of course, it could be some idiom unknown to me, in which case I would have no idea about it.

By the way, there is a modern idiom "etwas/ein Ass im Ärmel haben", which means "having something/an ace hidden inside/up your sleeve". Maybe there's a connection there?

[gleaming sail]

its "Du hast in deines Ärmels falten den Mond getragen, ihn gespalten". I am not sure what ace in your sleeves means. The lateral meaning doesn't really make any sense either@patent reef

[patent reef]

"having something up your sleeve" means having a hidden trick to win (it's from playing cards as a conman, having an extra ace up your sleeve means you can switch out cards in your favor as a trick).

Literally I'd say it translates to "You carried in your sleeve's folds the moon, broken/split it [the moon]." But I have no idea what it might refer to.

After I looked up the excerpt, I now know it's from Beethoven's "ruins of Athens", the "allgro ma non troppo, dance of the Dervish". From the rest of the text, I'd assume it's referring to something related to Muhammed and the Quran. But I have no idea what specifically is meant by this.

I looked for passages of the Quran about the moon, and I think it might refer to this: https://en.wikipedia.org/wiki/Splitting_of_the_Moon

Later I discovered this text: https://www.academia.edu/39932374/_You_Carried_the_Moon_in_the_Folds_of_Your_Sleeve_A_Note_on_Wide_Sleeved_Garments_from_Arabic_Sources_ But I haven't taken a closer look at this.

[gleaming sail]

I dont think "you carried the moon in your sleeve" is something commonly said in arabic lands perhaps turkish but not arabic. Anyways can you confirm that this is not a German expression whatsover? not even an old one?

[vestal gulch]

Nobody claimed it was an Arabic saying/expression. And no, to my knowledge, it's not a German expression, not even an old one.

[gleaming sail]

Uh What is it that make you so sure that it is not a German idiom? I mean german guy made the music and another german guy made the play before it. It was written in germany so german people could understand at that time.

Was made up expressions a thing in 1800s?

[gleaming sail]

To your knowledge, not every German expression that you don't know is a non-German expression

[vestal gulch]

I was being polite/careful by saying "to my knowledge". It is not a German expression. Whether you believe me or not is up to you.

[gleaming sail]

It is not about believing. This is not religion. This is linguistics with facts and evidence. Making claims is not going to answer my question. If you have evidence for that, please put it forth.

[vestal gulch]

Best of luck with finding proof for the non-existence of... well, pretty much anything.

😹

[patent reef]

The thing is, you have a sentence. Some sentences are idioms, but - and that is important to stress - not every sentence is an idiom. Some sentences that are in fact idioms are idioms in ways that are more obvious to a native speaker than others. And some sentences were idioms at some point but are not anymore. To the best of @vestal gulch 's knowledge, and to mine as well, it's at least not an idiom that has been in use for the last decades, and doesn't seem to us a likely candidate for an older idiom. We (or at least I) are/am no linguists, so there is some room for error there, but while we have less authority or background knowledge in these things compared to a linguist, we most likely have more than you. If that isn't enough for you, we can't help you, and you should probably write to a university professor who deals in these things.

By the way, not all in linguistics is facts, as language is ever changing, so there might be - for example - different opinions in what a common phrase is and what is not, depending on regional or personal contexts etc.

[patent reef]

Making up expressions is a thing I'd say every language does all the time. Some expressions stick, and those are called idioms. If they don't stick, they're just stuff someone said.
And there's especially a lot of making up stuff in music.

German poet Friedrich Schiller made up so many expressions/idioms in his poem "Das Lied von der Glocke" that generations of German schoolchildren had to memorize the poem (see the section of the German wikipedia article just about his made-up expressions from that poem: https://de.wikipedia.org/wiki/Das_Lied_von_der_Glocke#Geflügelte_Worte_aus_der_„Glocke“)

[gleaming sail]

Thank you. this is honestly a much better unswer than "it is not german. whether you believe me or not up tp you"

Also, ofc not all linguistics is facts as with all scientific fields, they are changing continuously based on theories accepted and denied and the ones that deal with statistics.