For centuries in England, January 5 was Twelfth Night Eve, the last night of the Christmas season before Epiphany, celebrated with wassailing, cake-cutting, and traditions of role reversal where servants and masters swapped places for an evening. Shakespeare's play, likely written around 1601, took its title from these revels.
Long before it was flattened into a single word on modern calendars, Twelfth Night carried real cultural weight in early modern England. It marked the end of the twelve days of Christmas, and January 5 eve was when households held their final blowout before returning to ordinary winter routine and taking down the greenery that had decorated homes since Christmas Eve.
The customs were riotous by design. A special cake was baked with a bean and a pea hidden inside; whoever found the bean in their slice became King of the Bean for the night, and whoever found the pea became Queen, regardless of their actual social rank. For one evening, a servant might command their master, and the usual hierarchies of Tudor and Stuart England were cheerfully, temporarily dissolved. Wassailers went door to door singing for spiced ale, orchards were 'wassailed' to encourage a good fruit harvest, and mumming plays were performed in village squares.
Shakespeare's Twelfth Night, or What You Will, first performed around 1601-02, borrowed this spirit of festive inversion and gender confusion directly from the holiday's traditions—Viola disguised as a man, a household turned upside down by revelry, is Twelfth Night's chaos rendered as comedy.