The name is derived from the Franzhagen Castle in Schulendorf in the duchy of Saxe-Lauenburg.
The castle was inherited by Eleonore Charlotte of Saxe-Lauenburg-Franzhagen, who brought it into her marriage with former Duke Christian Adolph I.
After their bankruptcy, the Sonderburg line was reduced to its possession of Franzhagen.
The real power of government from 1702 was wielded by Eleonore Charlotte of Saxe-Lauenburg-Franzhagen, the widow of Christian Adolf I, as the sons had married beneath their station.
Anna Barbara Dorothea of Winterfeld never owned more than a house in Billwerder, until her death in 1739.