Here's another expression - bad scrans to the hoof - here's the context -

Worst luck of all was yet to come. On the morning when Darby went for the cow to bring her into market, bad scrans to the hoof was there; but in her place only a wisp of dirty straw to mock him.

I can understand that it means bad luck in some way, can anyone explain it?

It's followed by - Millia murther! - míle murder, would that be? unless murther is another word transcribed from Irish.

Ballyraggin' - what does that mean? - insultingly?

a nearby bullfrog called loudly an' ballyraggin' "The Omadhaun! Omadhaun! Omadhaun!" it said (obviously - amadán)

It's an old saying:
bad scran to … means "bad luck to …"
(By the way, it's scran not "scrans" in that particular saying)

murther is just another way of saying the more standard word "murder"

To ballyrag somebody is "to scold" or "to verbally abuse" somebody.

You don't run across these sorts of expressions very much anymore – more's the pity!

Yes, these expressions are Hiberno-Irish, used long ago and seldom heard now, I imagine the author used Slieve na Mban as it is a real place name to give feeling of folklore to her story and I feel that the story is her own creation.

According to what I've been able to find, that's the case. The stories are her creation, not folklore.

Redwolf

These stories may will be of her own making, but they're certainly based in an Irish context and she knows how to tell a good story.
Anyway here's another word - moil - as in:

Take my adwice - nayther make nor moil nor meddle with the fairies -
would that have anything to do with - moill?

a caubeen - is some kind of a hat, but is it as Gaeilge?

Ochone mavrone - mavrone would be mo bhrón but ochone, is that simply an interjection or another word?

Moil - I assume that's "moill". Ná déan moill. Don't stick around.

Caubeen, probably Caibín - The dictionary says -
1 Tá caibín air ó chaill sé na fiacla, his mouth has sunk.
2 a prominent chin
3 a goatee
4 edge of blade

ochone = óchón - a cry of lament, "alas", like in the song "Caoineadh na dtrí Muire".

_________________
___________________________________________________________

It is recommended that you always wait for three to agree on a translation.
I speak Connemara Irish, and my input will often reflect that.
I will do an mp3 file on request for short translations.
___________________________________________________________

I wonder if "caubeen" was a mishearing of "caipín"?

The problem is that the author herself is somewhat removed from these terms. She grew up in an Anglo-Irish family, and spent most of her adult life in England and the U.S. She probably heard them, but I doubt she ever used them. Makes them harder to isolate.

Redwolf

Ah yes it could be that.
Here's another one - the priest isn't happy that Darby has set free from the Good People only those who are from his own parish, so he answers back -
"Would yer Reverence have me let out the Corkonians, the Connaught men and the Fardowns, I ask ye?" he says, hotly.
Who are the Fardowns, might I ask? and from where in Ireland might they come from?

I'm surprised that Lughaidh hasn't already answered this one.

A Fardowner is a person from the North – especially a person from Donegal.
By the way, I've only ever run across Fardowners, so I think "Fardowns" is probably not as common.

Go raibh maith agat a chara - but would you know why they call them Fardowns? - would 'down' come from dún, by any chance?
There's another word that I've managed to find, that I didn't know - dudeen - which means a small clay pipe - dúidín - but of course nowadays it means a joint as in dúidín draíochta (not that I would know anything about that, you understand) and - bheith ar dúidín ar réice means (or perhaps) meant to live the life of a rake.