Millions of Americans celebrate Halloween every year, though many may be unaware of its origins and meaning.

Halloween is an evolution of what was once the ancient Celtic festival of Samhain (pronounced sow-en, with sow rhyming with cow). It marked the end of the year, as well as the end of the harvest and summer for the Celts, who 2,000 years ago were based in the area that is now Ireland, the United Kingdom and northern France.

It was a significant celebration for the Celts because they believed that on this night, there was a mix of the worlds of the living and the dead and that the ghosts of the dead returned to earth, bringing about trouble and destroying crops. But they believed this mix also allowed predictions to be made about the future, an essential means of guidance for the lengthy, gloomy winter.

“When you are faced with a new year, you’re curious as to what the new year is going to bring for you, for instance whether you’re going to see death,” said English professor William Heim, who teaches Literature and the Occult.

Romans eventually conquered the Celts and ruled their land for 400 years. During this time, the Romans brought their own influences to the holiday. According to the History Channel’s Web site, Feralia, a Roman festival that commemorated the passing of the dead in late October, was intertwined with Samhain. Feralia was a day designated to honor Pomona, the Roman goddess of fruit and trees, whose symbol was the apple. Pomona is believed to be the inspiration for the favorite Halloween pastime of bobbing for apples.

“The bigger the apple, the more it says it’ll be a prosperous year for you,” Heim said.

The Roman-influenced Samhain would eventually be further remolded by the Roman Catholic Church. In the seventh century, Pope Boniface IV chose to acknowledge saints and martyrs by establishing All Saints’ Day on Nov. 1. The day was also called All-hallows, and Samhain began to be known as All-hallows Eve and eventually, Halloween. All Souls’ Day, a day to honor the dead, followed All Saints’ Day beginning in A.D. 1000, when the church formalized it. The three festivals together were known as Hallowmas.

“The church was trying to channel the interest to the saints,” Heim said.

The History Channel’s Web site also states that the Protestant church discouraged the holiday, deterring European immigrants from practicing their Halloween celebrations and customs in early New England, though it was common in the South.

As America began to evolve, it fashioned its own version of Halloween, beginning with parties celebrating the harvest through dance, song, fortunetelling and storytelling.

When the Irish arrived in the United States in the second-half of the 19th century, they brought with them their own take of the holiday, which eventually became known as “trick-or-treating.”

Trick-or-treating could have originated from All Souls’ Day, which was celebrated with parades as was Samhain, when the poor in England would “go-a-souling” for “soul cakes,” pastries received in exchange for the promise to pray or a family’s dead relatives. Eventually, children began to take on the task of “going-a-souling” door-to-door and were given ale, food and money as the origin of this favorite Halloween pastime.

But Heim believes the origin of trick-or-treat may be Scottish, not Irish or English.

“Children collected combustibles to feed bonfires in the 19th century by going door-to-door saying, ‘A piece of peat to burn the old witch,'” Heim said.

Still other theories suggest that treats were given to deter mischievous children from playing pranks.

In any case, trick-or-treating, along with the holiday, has grown into an almost $7-billion industry in this country, according to National Geographic’s Web site.

However, in Spanish-speaking countries, such as Mexico and Spain, Halloween remains a spiritual day known as El Dia de Los Muertos, the day of the dead, which celebrates a three-day observance to honor the dead. Many families prepare for the return of dead loved ones by constructing altars in their homes made up of things such as photographs, food and water.

The return of the dead hasn’t always been welcomed, but is a holiday people always have been prepared for. A similar ancient tradition existed where families would leave bowls of food outside the home to appease ghosts and prevent them from entering, Heim said.

“On the one hand, you’re always glad to see your dead relatives, on the other you don’t want ghosts roaming about your house,” Heim said.

Still another way to deal with the ghosts was to dress up like them, Heim said. Although costumes sometimes served as a representation of the spirit of the departed, they were mostly worn as protection against evil spirits.

“Evil spirits are afraid of things that look as ugly as they do,” Heim said.