A settlement of servants and manual workers grew up around the castle and this became the village of Castlethorpe (thorpe is an Old Norse language (particularly Danish) word for homestead, and it is not unreasonable to assume that there may well have been a Danish settlement nearby as the area was, if not part of, certainly close to, the Danelaw).
Dunstan's farm, name of an Anglo-Saxon farmer who came from danelaw with the danes, probably in the 10th century, to settle in Normandy.
The disparate nature of manorial holdings and local laws mean the Free Tenant in Kent, for example, may well bear little resemblance to the Free Tenant in the Danelaw.
The first part of the name is believed to be the Old Norse word thorp with the meaning outlying farm, indicative of the village's location within the Danelaw.