Like many, I have hard-to-find ancestors whose children immigrated from Ireland. I have a story handed down that my 3x great grandmother was catholic, from a wealthy family and in love with a man who was protestant and they were forbidden to see each other. So they did what any hot-blooded young couple would do, they eloped! I don't know if they married in Ireland or somewhere in the UK, on a ship, or in Canada, but they first show up in records when they had their first child, my 2x great grandfather in 1840 in Quebec.
I have other ancestors from Ireland that are maybe not as interesting, but just as hard to find.
The other day I came across this interesting book:
Varieties and Synonymes of Surnames and Christian Names in Ireland: for the guidance of registration officers and the public in searching the indexes of births, deaths, and marriages
It gives variations of spelling, names from English to Irish, abbreviations or nicknames, etc, then pages of Surnames with variants.
You get about half way through the book and find it is two books for the price of one! The Second half is titled "Authorship and Publication: a concise guide for authors; including the law of copyright" - it is also quite interesting, with info on everything from titles, choice of paper and size of type to bookbinding, publishing and copyright.
Hopefully this book will help you in your quest to find those elusive Irish ancestors, and give you some sage advice when it comes time to publish your genealogical findings.