This extract is from Dr. Ciarán Ó Duibhín's great research, 'The Irish Language in County Down'.
It is available to downland here.
Here are his conclusions on the nature of County Down Irish.
"County Down Irish: the nature of the dialect
It is hardly surprising that Down was the earliest Ulster county to lose the continuous thread of native Irish over its whole area when we consider how it is situated near to major commercial centres and trade routes. The Mourne Mountains failed to protect the language as effectively as did more modest hills elsewhere in the province. Irish in County Down did not survive until the age of sound recording: I do not know of a single word of it on tape or on record. It did not survive into the golden age of folklore collection: little of it has been noted in the form of popular stories, songs or proverbs. It did not survive into the age of descriptive linguistics, when a scholar could write down a scientific description of speech which would enable another to recreate it at a later time. Given another fifty years, all of these things would have been different. In spite of all this, we still know something of the nature of County Down Irish, for example, from the consideration of placenames, and from its evident similarity to the longer-lived Irish of adjoining counties.
Ulster Irish occupies a central position in the Gaelic world made up of Ireland, Scotland and the Isle of Man.[i] Within Ulster, the main subdivision is into Donegal Irish and East Ulster Irish, the latter spoken until recent times not only in Oirghialla but in Inishowen, the Sperrins, the Antrim Glens and Rathlin Island. Being spread over such a relatively large area, East Ulster Irish must necessarily contain some variation, but nevertheless exhibits many consistent features.[ii]
One of the most striking differences between East Ulster Irish and Donegal Irish is the pronunciation of the vowel written ‘ea’ (e.g. fear, a man, pronounced ‘far’ in most of Ireland, but as ‘ferr’ in East Ulster). Examples seen in English include the pronunciation of ‘Crossgar’ as ‘Crossgerr’, or ‘Kilfedder’ for ‘Giolla Pheadair’. J. J. Kneen comments that ‘it is interesting to find that Manx agrees with Scottish Gaelic and the Irish of County Down in retaining the short e sound in a word like “fer”, whereas elsewhere in Ireland it becomes â.’ Colm Ó Baoill shows that an e-sound (open or closed) is common all over East Ulster.[iii]
Another interesting case of the pronunciation of ‘ea’ is the name Seán—earlier spelled Seaghán—which is pronounced ‘Shawn’ in Munster, ‘Shaan’ in Donegal, but ‘Shane’ in East Ulster, whence anglicisations like Shane O’Neill, Shane Bernagh, Shane Crossagh, MacShane, Glenshane, Broughshane, and so on. Likewise Eachach, giving Loch nEachach (Lough Neagh), Uibh Eachach (Iveagh). The pronunciation of the second syllable of ‘Lecale’ seems to suggest that ‘a’ could be raised even after a non-palatal consonant; it may be no more than coincidence that this happens in southwest Scotland in words such as math, and is considered nowadays to be a characteristic of Islay Gaelic.
Cathal and Eachach also show that ‘th’ or ‘ch’ in the middle of a word tends to disappear and leave a single long syllable. Wagner adds the examples droichead and frithir, and Neilson advances athair and máthair, where the ‘th’ is omitted ‘in most of the counties of Ulster, and the east of Leinster’,[iv] At the end of a word too ‘ch’ can be very weak: ach (ah), fliuch (flooh), bocht (bot, as in Ballybot). Neilson says this last case occurs ‘in all the country along the sea coast, from Derry to Waterford’.
Neilson also states that ‘the ancient pronunciation’ of broad ‘bh’ and ‘mh’ as ‘v’, especially at the beginning or end of a word ‘is still retained in the North of Ireland, as in Scotland, and the Isle of Man’, whereas ‘throughout Connaught, Leinster and some counties of Ulster, the sound of “w” is substituted’.[v] An tAth. Mac Thréinfhir cites a Co Down place-name, Páirc a’ Bhóthair, which supports this. Neilson admits that broad ‘bh’ or ‘mh’ may become ‘w’ in the middle of a word, e.g. leabhar, but criticises dropping them in ‘the south’ in foghmhar and faobhar, which he says should have a ‘v’ sound.
Medial ‘ng’ is vocalised, e.g. in ceangail. Deartháir is shortened to dreár.
In the field of grammar, cha was universally used for negation in East Ulster, at least orally, though Neilson and the Tóruidheacht (in the manuscript) generally avoid it. Typical East Ulster forms of prepositions which turn up in the Tóruidheacht include ann a dteampoll (i dteampall), and roimhe leis an bheathaidh (roimh an bheathaidh). A characteristic East Ulster plural termination is found in tonnógadh, scológadh, etc.
Vocabulary items generally associated with East Ulster include coinfheasgar (tráthnóna, evening), tonnóg (lacha, duck), ársuigh (innis, tell), frithir (nimhneach, sore), corruighe (fearg, anger), práinn (deifir, hurry), go seadh (go fóill, yet), márt (bó, cow), toigh (teach, house).
A number of the peculiar features of East Ulster Irish are in agreement with the Gaelic of Scotland and of the Isle of Man. It has long been argued whether Rathlin Gaelic should be classed as Scottish or Irish, and Robert McAdam stated of Antrim Gaelic in 1873: ‘having myself conversed with both Glensmen and Arran men I can testify to the absolute identity of their speech’.[vi] A similar relationship must have held between the Irish of the Ards and the Gaelic of Galloway, and between the speech of Lecale and that of Man, but by and large County Down Irish may be taken as closely resembling the dialects of Armagh and Louth, where Irish was spoken well into the 20th century on the very borders of County Down. Similarity with Omeath Irish has been directly reported by Mac Gréacháin.
[i] For general information, see O’Rahilly, Irish dialects past and present (Dublin, 1932, 1972), chapter xvii; Colm Ó Baoill, Contributions to a comparative study of Ulster Irish and Scottish Gaelic (Belfast, 1978); Cathair Ó Dochartaigh, Dialects of Ulster Irish (Belfast, 1987); and, for more specific information: Mac Thréinfhir, ‘Gaeilge Chontae an Dúin Theas’; Mac Con Midhe, ‘Gaeilge an Dúin, II’; Dónal Mac Aonghusa, ‘An Ghaeilge i gCondae an Dúin’ in Lá, 25 March 1993, p 20
[ii] A number of the examples which follow are taken from a radio broadcast by Heinrich Wagner, date unknown
[iii] Ó Baoill, p 303
[iv] Neilson, part 1, p 143; Wagner, loc.cit.
[v] Neilson, ibid
[vi] Quoted in Patterson, p xi"