In what century did the land surrounding the Grand Duchy of Lithuania come to existence?
Lithuania proper:  The primary meaning is identical to the Duchy of Lithuania, a land around which the Grand Duchy of Lithuania evolved. Duchy of Lithuania: Duchy of Lithuania (Latin: "Ducatus Lithuaniae" ; Lithuanian: "Lietuvos kunigaikštystė" ) was a state-territorial formation of ethnic Lithuanians, that existed from the 13th century until 1413.
13th century