The Frisii were an ancient tribe, living in the low-lying region between the Rhine–Meuse–Scheldt delta and the River Ems, sharing some cultural and linguistic elements with the neighbouring Celts. The newly formed marshlands were largely uninhabitated until the 6th or 5th centuries BC, when inland settlers started to colonize the area. As sea levels rose and flooding risks increased, the inhabitants learned to build their houses on village mounds or terps. The way of life and material culture of the Frisii hardly distinguished itself from the customs of the Chaucian tribes living farther east. The latter, however, were considered to be part of the Germanic tribal confederation.

A terp, also known as a wierde, woerd, warf, warft, werf, werve, wurt or værft, is an artificial dwelling mound found on the North European Plain that has been created to provide safe ground during storm surges, high tides and sea or river flooding. The various terms used reflect the regional dialects of the North European region.