(frisian Upstalbeam)
During the 12th to 14th centuries, representatives of the Frisianregions, along the North Sea coast, assembled near the city of Aurich (Eastern Frisia, Germany) on the Tuesday after Pentecost to discuss matters of common inter est. This loose organization was not very effective, because it lacked the power to exact obedience to its decisions (willekeuren).
Historical Dictionary of the Netherlands. EdwART. 2012.