What is "saldern"

Saldern (up to the 17th century, Salder) or von Saldern, is the name of an old German aristocratic family from the areas of Hildesheim and Brunswick Land. The family seat of the same name is an eponymous castle on the River Fuhse in Salzgitter- Salder. Originally the family, whose branches are still alive today, only owned estates in the Lower Saxony area, but from the middle of the 16th century they also owned extensive property in the March of Brandenburg.