1938 changing of place names in East Prussia
On 16 July 1938, more than 1500 place names in East Prussia were changed, following a decree issued by Gauleiter and Oberpräsident Erich Koch and initiated by Adolf Hitler. Most of the names affected were of Old Prussian, Lithuanian and Polish origin; they were either eliminated, Germanized, or simplified.
Source: Wikipedia — 1938 changing of place names in East Prussia (CC BY-SA 4.0)