In ancient Greece, a wild drunken party was called a Bacchanalia. Specifically, a Bacchanalia celebrated the god of wine.
When the noun Bacchanalia starts with a capital B, it means the Greek festival honoring Bacchus, the god of wine, wine making, and the grape harvest. This festival, not surprisingly, involves a lot of wine drinking. Bacchanalia clearly comes from the name Bacchus — Bakkhos in Greek — and when it's not capitalized, it can refer to any crazy party, especially if alcohol is involved.