Every Swiss citizen inherits from his parents not only his family name and the citizenship of the Swiss Confederation, but also the citizenship of his ancestors’ home town and canton. This system of multiple citizenships came into use from the beginning of the modern era and is still operative today. The family names of all Swiss citizens alive in 1962 were collected in the Familiennamenbuch der Schweiz. There the surnames are listed in alphabetical order followed by all the communities whose citizenship a given family bears together with the year in which citizenship was granted, including even a possible former citizenship. Hence, this register provides an onomastician with lots of exact historical data which he would have to look for in a much more complicated and less reliable way in other countries. The aim of our contribution is to suggest several possible directions for research based on this register, e. g. the geographical distribution of surname variants (Gysi/Gysin, Maier/Mayer/Meier/Meyer), and different directions of internal migration movements from the Middle Ages onwards.