Sometimes in our search to find birth places in Ireland, we forget about wills. When people died leaving an estate, this becomes a legal matter. If there was family left in Ireland, then something may have been left to them. As a result their residence in Ireland is named.
This doesn’t necessarily mean this is the birth place you are seeking. This is where you have to be careful. Perhaps the immigrant’s siblings married and moved further away. This would especially be true with sisters. At that point, you would need to trace out their lives and see if that leads you to the birth place for all the siblings.
This strategy works especially well when the parish registers in Ireland have either been destroyed or they do not begin early enough to help in your research. It also works very well in the colonial period of North America as many people still had some active ties to Ireland. If colonial wills have been published in a book, then perhaps the index has a place name section.
When we are talking about wills, you have to keep in mind that only certain classes of people left wills. They are not always the wealthy, but average people having enough to generate a will. Also, keep in mind that if your family started poor upon immigrating, this doesn’t mean they remained poor. So keep an open mind about when to look for wills and when to move on to another record source.
Do not neglect wills for the siblings of your ancestor who also immigrated. They may also have mentioned the family in Ireland. This is why it is important to take the entire family unit, and research them out. The moral to the story of immigrant wills and Irish birthplaces, is to ALWAYS look for them.