Wikipedia
The Gediminids (, , , , ) were a dynasty of monarchs in the Grand Duchy of Lithuania that reigned from the 14th to the 16th century. One branch of this dynasty, known as the Jagiellons, reigned also in the Kingdom of Poland, Kingdom of Hungary and Kingdom of Bohemia. Several other branches ranked among the leading aristocratic dynasties of Russia and Poland into recent times.
Their monarchical title in Lithuanian primarily was, by some folkloristic data, kunigų kunigas ("Duke of Dukes"), and later on, didysis kunigas ("Great/High Duke") or, in a simple manner, kunigaikštis. In the 18th century the latter form was changed into tautological didysis kunigaikštis, which nevertheless would be translated as "Grand Duke" (for its etymology, see Grand Prince).