Wikipedia
Masurians
The Masurians or Mazurs (, ) were a Lechitic sub- ethnic group in the present-day Warmian-Masurian Voivodeship, Poland. They were descended from Masovians (; ), Polish settlers from Masovia who moved to Prussia during and after the Protestant Reformation, and who were primarily Lutheran.
In the 19th century, the Masuria region of East Prussia was named after the Masurians.
After World War II many Masurians were classified as Germans and expelled to West Germany or emigrated after 1956.