Mazurian ethnic group

The Masurians or Mazurs (Polish: Mazurzy, German: Masuren, Masurian: Mazurÿ) are a Lechitic sub-ethnic group in the present-day Warmian-Masurian Voivodeship, Poland. They are descended from Masovians (Polish: Mazowszanie; German: Masowier), Polish settlers from Mazovia 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 most of them expelled to West Germany or emigrated after 1956. They spoke Masurian dialect.

In the Middle Ages, the inhabitants of the Duchy of Masovia were called Mazur(z)y in Polish. Between the 14th and 17th centuries, Polish settlers from northern Masovia moved to the southern territories of the Monastic State of the Teutonic Knights. (These lands had previously belonged to the Baltic Old Prussians, whom the Teutonic Knights had conquered in the 13th and 14th centuries.) The northern part of this state was soon settled by settlers from Germany and thus became Germanised. On the other hand, the incoming Protestant from the until 1526 independent Duchy of Masovia, partially Polonised a southern part of the Duchy of Prussia, later Kingdom of Prussia. Only in Allenstein, now Olsztyn, Catholics remained, because it belonged to the Prince-Bishopric of Ermland or Warmia.

...
Wikipedia