While one can never be completely sure why Shakespeare titled his plays as he did, it can be assumed that Twelfth Night refers to the Eve of Epiphany. This was a holiday celebrated twelve days after Christmas to commemorate the Magi’s arrival to visit the baby Jesus.
Unlike most celebrations within the Church of England, the Eve of Epiphany was celebrated with much merriment, suspension of rules, and even the allowance of servants to mix with their masters. Some traditions would elect a Lord and Lady of Misrule, who would lead the drinking and the partying. These parties would also include disguises, so no one’s social class was truly known. By being Lord or Lady of Misrule, or due to a good disguise, low-class citizens would obtain somewhat of a higher rank for the duration of the celebration regardless of their actual social class.
This night of lawlessness makes for an excellent reference to the madness of the play. Servants attempt to court their masters, masters fall in love with their servants, drunkenness abounds, and very little order is found within the play. There are a few characters who could certainly be thought to be representatives of the Lord or Lady of Misrule. Feste, Sir Toby Belch, Sir Andrew Aguecheek, and Maria, all play crucial parts in the silliness of the plot. Many characters also wear disguises or specific costumes for a variety of reasons, which is something that happened a lot during the Eve of Epiphany.
While there is no specific reference or connection to the Eve of Epiphany within the play, Twelfth Night can be seen as a representation of it. Order is lost within the very first scene and is only found again with the play's close, when identities are revealed and the many plotlines are finally connected. It has been suggested that the song at the end of the play is a symbol of the reintroduction of reality. Now that the fun of the play is over, the audience must return to regular life—much like the return to social norms that participants of the Eve of Epiphany must face when the celebration ends.
By titling it Twelfth Night, Shakespeare was likely preparing audiences for a show of fun, madness, and hilarity, the same thing they would expect at the celebrations that fell on the twelfth night of Christmas.