Holstein · proper noun1
From a tribe which inhabited the area, the Holsten / Holtsaten. The name is equivalent to German Holz (“wood”) + Sassen (“inhabitant”), German Low German Holt (“wood”) + Saten (“inhabitant”).
Holstein · noun2
From the animals' region of origin: the horses came from Schleswig-Holstein, the cows came from the area of Frisia and Holstein.
Etymology from Wiktionary, CC BY-SA 4.0.