There is an interesting map called “Geo-Geneology of Irish Surnames”. 

http://tinyurl.com/y8hs9sw  In the 2009 ESRI International User Conference it won two awards in the Map Gallery Competition. It was placed first in the “Most Unique” category, and it won the People’s Choice Award. In addition, it received special recognition by the Cartography Special Interest Group. 

It was compiled by Dr. Kenneth Field, Principal Lecturer in Geographical Information Systems at Kingston University London, and Dr. Linda Beale a Research Fellow in the Department of Epidemiology and Public Health at Imperial College London. As you can see from the legend, this map shows the number of people in 1890 who had various Irish surnames. The larger the font, the more people who had that surname.  You can read more about it at http://www.esri.com/mapmuseum/mapbook_gallery/volume25/cartography/cartography-1.html and download a copy of the map at http://www.esri.com/mapmuseum/mapbook_gallery/volume25/pdf/mapbook25_22.pdf