https://en.wikipedia.org/wiki/Polans_(western)
The Western Polans (also known as Polanes, Polanians; Polish: Polanie, derived from Old Slavic pole, "field" or "plain", from Proto-Indo-European *pleh₂-"flatland") were a West Slavic and Lechitic tribe, inhabiting the Warta River basin of the contemporary Greater Poland region starting in the 6th century. They were one of the main tribes in Central Europe and were closely related to the ...