What is "goplans"

The Goplans or Goplanes (, ) was an early West Slavic tribe that inhabited the central parts of the Kujawy region, with their probable seat at Kruszwica. They might have been named after the Lake Gopło; Kmietowicz believes the Bavarian Geographer (845) overheard it and recorded it (as Glopeani). Many remnants of small strongholds have been unearthed around the lake. The tribe was absorbed by the Polans in the 10th century.