I also learned that this same person is from Dvinsk, Russia. This is very exciting for me. I did a little research and the lovely wikipedia took me here: http://en.wikipedia.org/wiki/Daugav
After reading this little bit:
The town's history began in 1275 when the stone castle Dinaburg (Dünaburg) was built by the Livonian Order in the lands nominally controlled by the Grand Duchy of Lithuania. In 1561 it became part of the Polish-Lithuanian Commonwealth (see: Duchy of Livonia) and in 1620 became capital of the Inflanty Voivodeship, which existed until the First Partition of Poland.
From 1784 onwards, the city had a large and active Jewish population  with proeminent personalities.
As part of the Russian Empire it was called Borisoglebsk (1656-1667) and Dvinsk (1893-1920). The town was renamed Daugavpils in 1920 as part of independent Latvia. The city was the site of the Battle of Daugavpils from 1919 to 1920. Dvinsk was part of the Soviet Union 1940-41 and 1944-1991 and Nazi occupied from 1941-44. The town was the scene of fierce Jewish resistance during those years. During the Cold War it was the site of the Lociki air base, 12 km northeast of the town itself.
I have come to understand why it is so difficult for Ashkenazi Jews to say what their heritage is! Common response: "It depends"! :)