I noticed there did not seem to be a thread about conlang idioms, so I guess I'll just have to start it! I've always been fascinated by the way idioms reveal something about our collective psyches...

Here are some Folkish idioms:
Ig kennist itt es mein namme (I know it like my name, meaning one is knowledgeable about the subject)
Itt'st regneth in troppen (it's raining in armies, it's raining a lot)

The traditional idiom of my conlang ceorzani is as follows: tirasema silwana arete d'ama.
Translated it means: The warrior silwana returns home.

Here is a couple in Værí:
Hévulis porļara ávet isacam. Translation: Hell's gates have opened. Meaning: This is going to be very bad.

Nam Narûv Resta ut rétius. Translation: And King Narûv will return. Used as an expression of sarcasm.

Toi hopekare namaja neseemus.
3ps river-against walk-INF attempt-PRES.PROG-3pm
He's trying to go upriver - a hopeless cause

Oh, we have them!

See here at the end of page: http://www.neoslavonic.org/lessons/11

cheers

Tikolmian has something about slipping on a banana peel, but I forget how it goes and what it means. Oh well, off to hit the hay. See you later. Be back when I have the idiom pinned down.

Here it is: zo xususuol lepas-is lemoxos rusayo (ibok).
[the banana-possessive skin-on step-inf many-time over]
Literally, it means "to step on the banana peel many times over". It's equivalent to "spinning one's wheels" or "going nowhere fast". The missing part is the idea that you're trying to not slip on it but you're just going to anyway no matter how many times you try. Also, ibok is unnecessary. The meaning isn't lost if you leave it out.

I just came up with this today. The original one is probably lost.

We haven't got any idioms in Leafoosish yet, but there is a saying: e'se bly fasil de ddir egyll ce dde sumeter se. It corresponds to the English "easier said than done", but the literal meaning is "it's easier to say needle than to submit [to one]". (I think you can guess what the reference is here -- what kind of needle do you "submit to"?)
And if you think that's dark and dreary on my part, you should see this thread!

Please, if you will, forget that. It was my feeble attempt at being imaginative and not just parroting the Welsh saying "haws dweud mynydd na mynd drosto" (easier to say mountain than to go over it, for anyone who's missed the discussions where it came up).
Since then, I've come up with an idiom that's only used in the three languages of Cymrygath, a city in the south of Llyffw. It's pretty much always the same: aler tros in Cymrygath Leafoosish (a dialect of my conlang), mynd dros (mynt tros' in the local "pinyin") in Cymraeg y cathod, and aller troche in the local French. It means literally "to go over", and it's a euphemism for "to steal". The fact that I came up with this is a sign that I've spent too much time thinking about the aforementioned mountain.

I've decided that the Leafoosish version of the mountain saying is ply fassil a ddír yfw ce atandre son ofrase ("easier to say door than to wait for it to open"). That's because they're cats and they hate closed doors.
Edit: And in case anyone's wondering what "Cymraeg y cathod" is, it's just a really weird dialect of Middle Welsh that's spoken by a few imaginary cats. It's not a conlang (as yet). If it were a conlang, I would probably refer to it by its native name, cymrāc y càith.