However it seems to be less well known that given ("first") names can also often have definite distribution patterns in Ireland. The dearth of Irish records from pre-Famine times leaves many genealogists of Irish descent up against a permanent "brickwall" as to the place of origin of their Irish ancestors. Anything that can provide any information is therefore valuable. Used in combination with the distribution of the surname, an unusual given name can help pinpoint a certain region of Ireland as a possible area of interest. Given names could perhaps be of more use in drawing focus to a certain area since there are several given names in every generation.Links are provided below to maps showing the distribution of a sampling of given names as shown in the Griffith Valuation. Some of them are clearly specific to a small region of Ireland (Johanna) - while others are more widely spread (Nancy).
Keep in mind that while a map may show that 2/3's of the occurrences of a name were in a region of Ireland of a few counties - that the odds are still "one-in-three" that your identically christened forebearer could have been born somewhere else. However most of the remaining occurrences were usually in adjoining counties.
There are some names used among the Irish so commonly as to probably be of no use in pointing out any one specific area. For the men: John, James, William, Patrick. For the women: Mary, Margaret, Bridget, Catherine.