Every family has their own traditions when it comes to how they celebrate Christmas Eve, but those who grew up in Italian-American households likely only know of one tradition—the Feast of the Seven Fishes.

The Feast, also known as Festa Dei Sette Pesci, is a Christmas Eve tradition that has become popular in many households.  The tradition is surprising not well known amongst all Italians because the different regions of Italy all have different traditions when it comes to their Christmas Eve, or Cena della Vigilia, dinners. It is believed to have started in the Southern regions of the country, before truly gaining its popularity in America.

The feast gained in popularity in the 1900s, as Italian-American families attempted to rekindle the traditions of the Old Country into their holiday meals, according to Eataly. That eventually evolved into the feast as it is known today.

The tradition of eating fish for the holiday stems from the Roman Catholic custom of abstaining from meat and dairy products ahead of the birth of the baby Jesus on Christmas Day. Since meat is not eaten during the fast until Holy Communion is received during Midnight Mass, Italians then began indulging in seven different types of fish as a substitute.

As for why the number is predominately seven, it is tied to symbols of Catholicism, though it’s unclear what exactly it represents. Some believe the fish represent the seven deadly sins, the seven days it took for God to create the earth, the seven sacraments or the seven virtues of Christian theology.

As for the menu that is offered for the feast, it varies from household to household, and there are no set rules for the kinds of dishes served. However, according to Bon Appetit, for those who are looking for some guidance while preparing their feast, there is some organization to the courses.

According to the magazine, the courses should include one that features a more snack-friendly dish, a nice salad, a hearty grilled dish, a pasta dish with seafood and a seafood stew.