In the mid nineteenth century, the Irish became the largest immigrant group in Britain. Despite impressions of homogeneity delivered by the dominant historiographies, these migrants were in reality complex and changing groups whose variegated nature has been underplayed by historians. One of the reasons why the Irish tend to be lumped together as an undifferentiated mass is the lack of systematic analyses of the particular regional and provincial provenance of those who made homes in England, Wales and Scotland. Historians speculate about origins; but few have interrogated the census to provide robust assertions about where in Ireland particular migrants came from. As such, complexity and subtlety are absent. The failure of the census systematically to capture specific birthplace data offers one explanation of why this is so. The sheer difficulty of abstracting data on birthplace to arrive at meaningful quantitative perspectives provides another. This essay uses a technique from biological anthropology called Random Isonymy which enables us to substitute surname data for birthplace data in order to establish the major interregional interconnections between the two islands which are evinced in Irish migration pathways. We show that the close association between name and place in Irish culture enables robust conclusions about the provenance of migrants to be derived from surname data drawn from the digitised 1881 census. Our work suggests that names may underpin cultural transfer, and thus could help explain why particular types of Irish culture emerged in one town or region but not in another. For now, this essay's discussion is restricted to an explication upon the robustness of the method.