Dionysus is the Greek god of wine, growing plants, and the wild joy — and wild mess — that can come with them. Stories connect him with drinking, parties, theatre, and sex, and with a kind of religious frenzy where people feel taken over by the god. The Romans called him Bacchus. In pictures he is often a young man with ivy or grapes, sometimes with a noisy band of followers. Though actually, he is not only a “party god”: in the old religion he also stood for how living things die back and return, and Greek drama grew out of festivals for him. When English speakers call a night Dionysian, they mean it was wild and uninhibited, full of drink and letting go — a slightly bookish adjective. The name is capitalised because it is a god’s name.