When people say "Irish tartans" what most readily springs to mind are the very popular Irish county tartans. These were designed by The House of Edgar in 1996. The House of Edgar is a Scottish tartan firm, located in Perth. In addition to all of the Irish county tartans, they also have designed the popular Irish National tartan. Lochcarron of Scotland, located in Galashiels, has designed tartans for all of the Irish provinces, as well as three different "All Ireland" tartans. Taken together, these two Scottish companies probably supply most of what people consider to be "Irish tartans" today.
Even historical Irish tartans seem to have at least some Scottish connections. The most famous is the Ulster tartan, taken from a suit of clothing, c. 1600, that was unearthed on a Dungiven farm in 1956. Textile experts believe that the tartan cloth was most likely woven in Donegal, Ireland, but shipped to the Highlands of Scotland to be made into trews!
But the real reason for this post has to do with many of the so-called Irish name tartans. While there are some that are legitimately commissioned and/or created by Irish families for use by those of the name, many of them seem to have been designed merely for fashion purposes (or perhaps even to fill an order from an Irish-named customer), and based off of pre-existing Scottish tartans.
One famous example is the Tara tartan, also sometimes called Murphy or O'Keefe. Like many of the Irish tartans on record, it was thought to have been included in the book Clans Originaux, published in Paris in 1880. However, recent research undertaken by the Scottish Tartans Authority has shown this work to be a tartan sample book of sorts, containing no Irish tartans whatsoever. Discounting this, the next earliest date we have for this tartan in 1967, when it was being sold to Irish customers by The Kilt Shop, in Edinburgh! It is interesting to note that this tartan is simply a color change of the MacLean of Duart. Both tartans are shown below for comparison.
MacLean of Duart tartan
Another example of the same sort of thing is the Clodagh tartan. The Scottish Tartans Society had a woven sample of this tartan, dating from 1970, from D. C. Dalgliesh of Selkirk. In 1979, a bagpipe maker from County Tyrone wrote to Alex Lumsden, researcher for the Scottish Tartans Society, saying that this tartan came from the Bog of Allan in southern Ireland. However, no other evidence of this being an "artifact tartan" has surfaced.
Another curiosity is that this same tartan was supposed to have been recorded as "Dowling" or "Bowling" in the Clans Originaux, c. 1880. But, as I stated, we now know that there are no Irish tartans in the Clans Originaux. STA notes also say that the woven sample in the STS records is from 1980, not 1970.
An important thing to note here is that this tartan is essentially a color change of the Royal Stewart. While it very well could be possible that this is what the Royal Stewart may look like after being buried for a couple of hundred years in a peat bog, and the man who unearthed it was named Bowling or Dowling, and therefore his name became associated with the tartan, I personally doubt it. There seems to be a tendency to create "Irish" named tartans by simply altering the colors of pre-existing Scottish tartans. My gut feeling is that this is simply another fashion tartan originating in the 1970s.
Changing traditional Scottish tartans to create new Irish ones seems to be a common practice that continues today. The Royal Stewart tartan seems especially popular. Other Irish tartans that have been designed as Royal Stewart variants are the O'Farrell and the Shaughnessy. The latter was designed by Scotch Corner, a company from Gateshead, England, that has designed many Irish family tartans, apparently on spec to meet customer's requests.
The final "Irish" tartan we will look at is the MacCormick tartan. This one dates to 1985 and was designed, apparently, by Pendleton Woolen mills in Oregon. Once more, it is the same sett as a pre-existing Scottish tartans, with a simple color change. In this case, it is a Campbell tartan that is being altered (though a shortened version of the usual Campbell sett -- this one has been recorded as Campbell, 42nd, and Sutherland and is included in Wilsons of Bannockburn's 1819 Key Pattern Book).
Before I close, I want to reiterate that there are indeed some Irish tartans that were designed by Irish people and are recognized as legitimate within Ireland. The most notable of these would be the Cian tartan, which was registered with the Chief Herald of Ireland in 1984 and is accepted and used by the Clan Cian Society. But one does have to admit that many of the so-called Irish tartans were created by people outwith Ireland, and actually have their origins in pre-existing Scottish tartans.
One final note: All images of tartans on this site are courtesy of the Scottish Tartans Authority. The settings of the different tartans are different sizes in most cases, and the images show only a portion of the tartan. Ideally all the images would be the same size and show the same portion of the design for comparison purposes, but that is a task beyond the time I have allotted for this post!