🔼The name Dionysius in the Bible
The name Dionysius occurs only once in the Bible. When Paul was in Athens, he debated Stoics and Epicureans and ended up preaching at the Areopagus on Jesus and the resurrection. Among the people he was able to convince were Dionysius the Areopagite and a woman named Damaris (Acts 17:34).
The name Dionysius denotes a belonging or pertaining to Dionysus, the Greek god of the grape harvest and thus wine and wine making, and thus wine drinking and subsequent excesses. Dionysus was known to the Romans as Bacchus.
In popular imagery, this deity is often depicted as a mere Chief Entertainment, but its significance as cultural phenomenon goes far beyond that, as the Bible obviously notes. When Noah exited the Ark, he planted a vineyard and became drunk. His son Ham ridiculed him, and Noah's subsequent curse organized the modern nations. And when Jesus prepared His disciples to make disciples of all the nations (Matthew 28:19), He instructed them to remember Him by drinking wine (Matthew 26:27).
🔼Etymology and meaning of the name Dionysius
The name Dionysus is very old and it's no longer clear what it may have meant to whoever first thought of it. The Dio-part appears to come from the same set of words that gave us the word dios and ultimately the name Zeus. It means Bright or Divine:
The second part of our name appears to derive from Nysa, a mythic mountainous land somewhere in Africa or even India, peopled by nymphs and such. However: the cult of Dionysius appears to have been introduced to Greece via the Hittites in Anatolia, and they called themselves the "Nesi".
The sixth century BC Greek philosopher Pherecydes of Syros surmised that both names Dionysius and Nysa derived from the word nusa, which meant "tree" in some very old language. Hence Dionysus was also known as Endendros, or "He in the Tree," which is also a frequently deployed image in the Bible: from the fruit of the paradisal tree (Genesis 3:6) to Absalom and Zaccheus and finally Jesus on the cross (Galatians 3:13).
Ultimately, the name Dionysius (and thus the derived name Dennis) means Belonging To The Light Of The Tree, or something along those lines.