DONJON means KEEP in French.

The term is derived from the Latin dominium, meaning lordship, signifying that part of a castle that was the ultimate strongpoint and refuge and contained the most prestigious residential accommodation for the lord himself.

It was thus an essentially feudal concept: as the inner sanctum of lordship it was regarded as the particular symbol thereof, and for practical and symbolic reasons it was given a structural and architectural emphasis to make it the main piece of the castle.

In French the word retains much of its original meaning, though confined to the tower keep, which is only one form of donjon, but in English, through a very early secondary usage (1186), it has come to mean a dark subterranean place of confinement.

The word ‘keep’, which has been adopted more or less as an English synonym for donjon in its original meaning, first appeared in the 16th century.

There are several types of donjon. The word was applied by contemporaries to the motte and its timber superstructure (palisade and tower) of those early castles constructed in the ‘motte-and-bailey’ form.

Surviving mottes, even denuded of all superstructure, can still be very impressive and were a formidable obstacle to attack; it is interesting and significant that on the late 11th-century Bayeux tapestry the motte is used as the symbol of a castle.

It is also clear from both literary and archaeological evidence that the timber tower within the palisade upon the summit was or could contain the apartments of the lord and could be surprisingly elaborate.