The seven red seeblatts (or pompeblêden, as they are called in Frisian) are a reference to the Frisian "sea countries" in the Middle Ages:[REF] independent regions along the coast from Alkmaar to the Weser who were allied against the Vikings.
The pompeblêden are used in other related flags such as the flag of the Ommelanden in neighbouring Groningen Province, a historically Frisian area, and for a proposed pan-Frisia flag put forth by the Groep fan Auwerk.