Ruthenian

Ruthenian is the South-Western branch of East Slavic, descended from the Old East Slavic of Kievan Rus and carried after the Mongol sack of Kiev in 1240 through the western Rus lands that fell to the Grand Duchy of Lithuania.

From the 1300s the chancery in Vilnius shaped it into the Grand Duchy's official language. All three Statutes of Lithuania, of 1529, 1566 and 1588, were written in it; Francysk Skaryna of Polotsk printed a Bible at Prague between 1517 and 1519.

After the Union of Lublin of 1569, the grand duchy gave up its chancery form of Ruthenian, Chancery Slavonic, for Middle Polish; the nobility Polonised, but the Orthodox peasantry kept the old speech. By the early 1700s it had split into early Belarusian and Ukrainian, both becoming separate standards by the end of the century, while the Carpathian highlands kept their own Rusyn vernacular.