Old Prussian

Old Prussian is an extinct Baltic language, once spoken by the inhabitants of the area that later became East Prussia (now north-eastern Poland and the Kaliningrad Oblast of Russia) prior to the German colonization of the area which began in the 13th century. In Old Prussian itself, the language was called “Prūsiskan” (Prussian) or “Prūsiskai Bilā” (the Prussian language). A few experimental communities involved in reviving a reconstructed form of the language now exist in Lithuania, Poland, and other countries.
See more at Wikipedia.org...

Noun
1. a dead language of the (non-German) Prussians (extinct after 1700); thought to belong to the Baltic branch of Indo-European
(hypernym) Baltic, Baltic language