'donjon' originates from Old French, specifically the word 'donjon', where 'don-' meant 'lord' and '-jon' referred to a 'tower'.

'donjon' changed from the Old French word 'donjon' and eventually became the modern English word 'donjon'.

Initially, it meant 'a lord's tower or residence', but over time it evolved into its current meaning of 'the main tower of a castle'.