During the Middle Ages personal names in Denmark became strongly dominated by Christian names that came into use with the introduction of Christianity from the 10th century and spread to all parts of society. The old Nordic names that had been used since the Viking Age are estimated to represent only 5-10% of the names by the end of the Middle Ages (i.e. 1536 in Denmark). The percentage only gets this high when the popular Nordic saint’s names Ole, Knud and Erik are included. However, name materials from the 1700s show that a number of old Nordic names were still used throughout the country, often locally concentrated and in descending frequency. Many of these names are extinct today, but some of them have lived longer than what may have been believed so far, and a few have survived continuously until today.
Personal names from Denmark from the earliest known sources containing personal names until the Middle Ages are thoroughly documented in the dictionary The Old Personal Names of Denmark (Danmarks gamle Personnavne 1936-64). Differently unspecified is the period after the Middle Ages, and until about 1900. The sources of this period's personal names are so extensive that it has not been possible to review the nationwide name use in Denmark before the country's inhabitants were registered electronically in the second half of the 1900s. However, it has become possible with the recent digitization of Danish censuses from the 1700s and 1800s. Thus, the infrequent names from that time that only rarely have been encountered in previous geographically and chronologically limited studies, have therefore become much easier to get knowledge of.
The oldest Danish census with the total population's names from 1787 along with the so-called Jessen Reports from the 1740s, which contain reports of rare personal names around the country, provide insight into the diversity and continuity of Nordic names that existed, but were hidden under a thick duvet of extremely frequent Christian names. This is the period before the so-called Nordic Name Renaissance, that with the national romanticism in the 1800s, resumed many Nordic names, now often used in a (adapted) Norse form, e.g., Gunhild, Gyda, Hakon, and Helge vs. Gundel, Gye, Haagen, and Helle. Based on a thorough examination of the two 1700s sources, the distribution and variation of the remains of the Viking Age's name system that was still used in Denmark in early modern times, will be uncovered.