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.
The Æsti, mentioned by Tacitus in his Germania, may have been a people who spoke Old Prussian. However, Tacitus describes them as being just like the Suebi (a group of Germanic peoples) but with a more Britannic-like (Celtic) language.
Old Prussian was closely related to the other extinct Western Baltic languages, Curonian and Sudovian. It is more distantly related to the surviving Eastern Baltic languages, Lithuanian and particularly Latvian, and to the Slavic languages. Compare the Prussian word zemē, the Latvian zeme, the Lithuanian žemė, the Russian земля (zemljá), and the Polish ziemia, all with the meaning of "earth" (soil).
In addition to the German colonists, groups of people from Poland, Lithuania, Francecitation needed], Scotland, England and Austriacitation needed] found refuge in Prussia during the Protestant Reformation and thereafter. Such immigration caused a slow decline in the use of Old Prussian, as the Prussians adopted the languages of the others, particularly German, the language of the German government of Prussia. Old Prussian probably ceased to be spoken around the beginning of the 18th century. The regional dialect of Low German spoken in Prussia, Low Prussian, preserved a number of Prussian words, such as kurp, from the Old Prussian kurpi, for shoe (in contrast to the standard German Schuh).
The language is called “Old Prussian” to avoid confusion with Low Prussian, a dialect of East Low German, and the adjective “Prussian”, which also relates to the later German state. The Old Prussian name for the nation, not being Latinized, was Prūsa. This too may be used to delineate the language and the Baltic state from the later German state.
Old Prussian began to be written down in the Latin alphabet in about the 13th century. A small amount of literature in the language survives.
Until the 1930s, when the Nazi government began a program of Germanization, and 1945, when the Soviets annexed Prussia and made Old Prussian place-names illegal, one could find Old Prussian river and place names in East Prussia, like Tawe, Tawelle, and Tawelninken.