The name "Skipsea" has Scandinavian roots and meant a lake that was navigable by ships. In the medieval period the site was an inland harbour, connected via a navigable channel to the North Sea, which in the 21st century is only around away. The surrounding region was referred to as an "island" during this period, due to the surrounding estuary and flood plains. The site of the castle was strategically important, as it lay on the main trading route through the marshes and was accessible by the sea; the castle had military and economic functions, being designed both to control the newly conquered Norman lands and to manage trade in and out of the inland harbour.