In An t-Oileánach, this is ní 'á bhreith as so é. Can someone explain the grammar of this?

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

The complete sentence would be:
Níl sé á bhreith as so. = It is not (being) taken away from here.
(present progressive, passive voice)

Probably the verbal noun was fronted:
Ní á bhreith as so atá sé. (or: … a bheidh sé, … a bheadh sé)

á bhreith = at-its taking, á refers to sé, so passive voice: it is being taken
as so = out of this, out of here, away from here

Then the verb bí was omitted (atá > Ø, the subject sé became é):

ní á bhreith as so é = it not (being) taken away from here.

It should not be taken away from here = Keep it dark.



Similar is the more common phrase:
Ní á chasadh leat é = it is not being reproached with you ("not that I blame you for it")
It appears in the same book a few pages earlier:
Dob’ aimilithe an bheirt iad, ní ’á chasadh leo é

EDIT:
Other examples
Ní á bhaint as do bhéal é = "not that I wish to interrupt you" (FGB)
Ní á éileamh é! = "not that I complain!" (FGB)
Ní á mhaíomh ort é, "not that I begrudge it to you" (FGB)
That is to be found in Cré na Cille, too: ní dhá mhaíochtáil ort é
Another one in Cré na Cille:
Ní dhá roinnt leis é, ní dhá roi(n)nt leo é
Ní á chur libh é (An Ghaedhilg sa Ghleann Gharbh)

I wonder if there are positive forms (is á ... é) and active forms (is/ní ag ... é)

It should not be taken away from here = Keep it dark.

How can "It should not be taken away from here" mean "Keep it dark"? And what does keep it dark even mean? Is this mean to mean "this should be kept secret"?

Ní á bhreith is a little strange, as there is no h-prefixation, but I think in traditional Muskerry Irish this would be: ní dhá bhreith.

Yes.
I got the impression that it's an English idiom, isn't it?
https://idioms.thefreedictionary.com/Keep+It+Dark
https://dictionary.cambridge.org/dictionary/english/keep-dark

FGB/EID has some translations for it (though not this one here).

I’d think - “not to be taken away from here” = “not to go beyond these four walls/this doesn’t leave here” = “keep it secret”.

Thanks Labhrás! I have some questions on the construct.


Everything that follows is a bit of a guess on my part, but bear with me for a second!
This part “the subject sé became é” strikes me as unusual in a fronted construction, but maybe you meant it’s how the construct has arisen historically?
Could it be the case that this is sort of a continuous briathar saor rather than the above?
To my ear the construct from the book sounds great, but it seems really similar to something like “chíthear dhom é” (it seems to me) in the sense that the é is grammatically an object form, but I suppose it’s really the subject of the sentence, with the object being referred to by way of a preposition.
So maybe the closest idiomatic translation is “it’s (the secret) not leaving this room”.

Thank you all

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

It is unusual. But it has parallels.
Its construction is: copula + small clause, the latter consisting of a predicative (á bhreith) and a subject (é), The result is: copula (ní) + predicat(iv)e (á bhreith) + subject (é), a "normal" copula sentence, like "Is fear é".

Á bhreith is a continuous/progressive construction (lit. "to-its taking", so either "taking it" (active) or "it being taken" (passive). Here it is the latter.
Progressive tenses require (normally) the verb bí, so a form like "atá" must be left out.



A saorbhriathar has always a synthetic verb ending (-tar, -far, -adh, -tí, -fí). But here is none.
Continuous tenses would require one of the saorbhriathar-forms táthar, bhíothas, etc. But here is non of them.
If we would say that it is atáthar that is left out, é would be superfluous, "á bhreith" would be active voice (taking it).



The grammatical subject of "Chíthear dom é" is in the ending -thear ("[some]one"). It seems to be a very idiomatic sentence at first glance. But it means simply: Not I see myself, but someone/something induces an impression on me, so Chíthear dom. É is object.



Yes, that is the intended meaning.

Could you elaborate? Why would ní á bhreith as so atá sé not work grammatically? Is it because the á bhreith 'being taken' is almost acting like an adjective, modifying (s)é?



Are you saying that if we were to use the autonomous form, the sentence would be nílt(e)ar á bhreith as so?

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I'm an intermediate speaker of the Corca Dhuibhne dialect of Irish and also have knowledge on the old spelling
Soir gaċ síar, fé ḋeireaḋ thíar

Oh, this is a misunderstanding.
Of course it works. It is the normal form.
The conspicuous absence of atá has to be due to the fact that it was obviously left out.



Yes.
Níltear á bhreith as so = One is not taking it out of here.

(But this cannot be the underlying sentence. That is: Níl sé á bhreith as so.)