The name came from Dionysus, the Greek god of wine, which is sometimes said to be derived from the Greek Dios (Διός, "of Zeus") and Nysos or Nysa (Νῦσα), where the young god was raised. Dionysus (or Dionysos; also known as Bacchus in Roman mythology and associated with the Italic Liber), the Thracian god of wine, represents not only the intoxicating power of wine, but also its social and beneficent influences. He is viewed as the promoter of civilization, a lawgiver, and lover of peace — as well as the patron deity of both agriculture and the theater.
Dionysus is a god of mystery religious rites, such as those practiced in honor of Demeter and Persephone at Eleusis near Athens. In the Thracian mysteries, he wears the "bassaris" or fox-skin, symbolizing new life. (See also Maenads.)
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 became modernised as Denys, then later as Dennis.
The name Sydenie (alternate spellings: Sydney or Sidney) may derive from a village in Normandy called Saint-Denis.
Denis is a very popular French name, common throughout the Francophone world, but is also a common English, Irish, German, Italian, Dutch, Croatian, Ukrainian, Russian, Bulgarian, Brazilian and Bosnian, Albania name.
Dionizy is the Polish version of the name.
Feminine versions of the name include: Denise, Denisa, Deni, Denice, Deniece, Dione, and Dionne.