As I learned more about Germany, I found that a lot of people, especially in Eastern Germany have names that almost sound Polish or half/Slavic. I was curious as to why. I did not know there was still a very small population of Slavs that still live in Eastern Germany or that the name "Berlin" was likely Slavic in origin.
So I got curious as to admixture levels. I found this:
It goes on to say:How can the profound stratification observed among East-German male lineages and their correlation with surnames be best explained? Although the name 'Germany' appears to imply a homogenous origin of the German people, the country has always been a gateway for migration, mostly from east to west. The best documented wave of migration was that of Eastern Germanic tribes and Slavs, driven by the Huns, that led to the downfall of the Roman Empire. In historic times, two major instances of assimilation of Slavic people into the German nation occurred. Around 950 AD, the German Empire started to put pressure upon the Slavic peoples inhabiting large areas of what was to become, in the mid of the 20th Century, the German Democratic Republic.26 By 1100 AD, after more than 100 years of wars and proselytization, the complete area of contemporary Germany had come under the influence of the German Empire. During the following centuries, most of the non-Germanic tribes (like the Baltic Prussians) completely abandoned their language, and their descendants are today regarded as 'typically German'. Only in a small area, southeast of Berlin, known as the Lausitz, the Slavic-speaking Sorb people maintained their language and culture, and their descendants today represent the only recognized, non-immigrant minority in East Germany. In any case, the names of many cities, including Berlin (meaning 'little swamp'), and some surnames, most notably those of 'typically Prussian' nature like 'von Clausewitz' or 'Virchow', still reflect the Slavic roots of this part of Germany. The second major assimilation of people with Slavic ancestry occurred during the Industrial Revolution in the 19th Century. Thousands of people from Eastern Europe migrated to the West to work in the surging industrial areas of Germany (Silesia, Ruhr-Area). Although they brought their surnames with them, they nevertheless became culturally amalgamated quite rapidly by the German majority.
The Halle region is located exactly at the intersection of the Germanic and Slavic spheres of influence of the 10th century, but it is also a traditional mining and chemical industry area (Halle-Leipzig-Bitterfeld) that has attracted Slavic workers during the Industrial Revolution. Both of these factors should have had an impact upon the male-specific genetic structure of the local population where surnames of Germanic and Slavic origin are about equally frequent. In terms of the relative importance of the two historic instances for the observed correlation between Y-STR haplotypes and surname characteristics, it is interesting to note that surnames first occurred in Europe in Venice during the 9th Century. From there, the law of name bearing was adopted in France and Catalonia in the 11th, and in England, and Western and Southern Germany in the 12th Century. In the North and East of Germany, the custom was practised no earlier than the 15th Century and, in some rural regions, surnames became fashionable only in the 18th century, nearly 900 years after their first appearance in Europe.27, 28 Furthermore, surnames frequently changed or became modified until the beginning of the 19th century. Therefore, it appears unlikely that the correlation between surnames and Y-STR haplotypes observed in our study dates back to the Middle Ages, but is more likely to be the result of the immigration of industrial workers in the 19th Century instead. In this respect, Central Europe appears to differ from England and Ireland where patrilineally inherited names are presumed to have a much deeper rooting.14, 15, 16, 17
The Halle samples were divided into three subgroups, according to surname. Two larger groups comprised 195 males with surnames that were definitely German ('G') and 185 males with definitely Slavic surnames ('S'). The third group contained 39 males with mixed German-Slavic surnames ('M'). Samples of 29 Sorbs19 and some 1313 published haplotypes from Polish males13 were used for comparison. Surname groups were defined on the basis of spelling, using certain combinations of consonants and surname suffixes to categorize the origin of the name in question. Suffixes '-er', '-mann' and '-burg', for example, are typically German whereas '-ke', '-ka', '-ow' and '-ski' are typically Slavic. In addition, the root morphemes of surnames were also examined. Examples for a Slavic root comprise 'Lessing', which sounds German but was derived from the Slavic expression for 'forest settler', and 'Kafka', which in Czech means 'jackdaw'. Mixed surnames include both German and Slavic elements, that is, a German basis and a Slavic ending, or vice versa ('Wudtke' or 'Kuppke'). These surnames are the result of a long parallel usage of both German and Slavic languages in the eastern part of Germany.
A similar characterization of the present samples in terms of the relative proportion of the fringe haplotypes resulted in highly significant differences between the two surname-defined German subgroups, G+M and S (chi2=13.094, 2 df, P=0.001). While 88 of the 234 haplotypes (38%) in the combined G+M group were classified as 'Western', this was the case for only 42 of the 185 haplotypes (23%) in group S. In contrast, 80 G+M haplotypes (34%) were of 'Eastern' type compared to 91 S haplotypes (49%). The portion of unclassifiable haplotypes was 28% in both groups (66 in G+M, 52 in S).
I found another article that calculate that 20% of surnames in East Germany are Slavic in origin, but I can't find it.