I reached out the the SCA Garb group on Facebook for more information about the Irish Overdress and a little bit of an SCA History lesson.
Some of the bits of the history lesson are quoted below. I have removed names, since the group is closed.
“’Irish Overdress’ was a RenFaire misinterpretation of some of Lucas De Heere’s prints of Irish Women which was adopted and stuck because there was so little to go on and so little research into Irish clothing. The Shinrone gown has some similarities in appearance but is of a much more complicated construction.”
One such print by Lucas De Heere.
Lady Sorcha Dhocair inghean Ui Ruairc’s packed on Irish women’s garb: [link]
A note on drawstrings and pleated sleeves as relates to the leine: [link]
The Honourable Baroness Ceara Shionnach of Burbage House’s information on Irish clothing: [link]
I feel it is important to mention that the “history lesson” part of the discussion included points that one should wear what makes one comfortable, how the SCA culture has changed in regard to authenticity, and not scary new people away. If you want to throw together some garb that can do double duty at RenFaires and SCA, or if you’re trying to stock your Gold Key with something quick and easy, then the “Irish Overdress” that’s available in commercial patterns easily found at your local craft store will work. If you want to portray a 16th century Irish woman, maybe do some more research.
Then again, I like research.
Go forth and discover! <3