Dionysus is a god of mystery religious rites, such as those practised in honour of Demeter and Persephone at Eleusis near Athens.
A mediaeval Latinised form of the Anglo-Norman surname Le Denys was Dacus, which correctly meant Dacian, but when the Vikings were about was often used to mean "Danish" or "The Dane".
The name Sydenie (alternate spellings: Sydney or Sidney) may derive from a village in Normandy called Saint-Denis.
It is also common as a German, Italian, Dutch, Croatian, Belarusian, Ukrainian, Russian, Bulgarian, Brazilian, Bosnian, and Albanian name.
Feminine versions of the name include: Denise, Denisa, Deni, Denice, Deniece, Dione, and Dionne.