Today, Halloween is celebrated in a number of countries around the world with costume parties, trick-or-treating, pumpkin carving and of course, endless amounts of candy. But many would be surprised to learn that the origins of Halloween go back almost two millennia!

Halloween as we know it today is an amalgamation of the Celtic celebration of Samhain with the Christian observance of Allhallowtide.

Samhain (pronounced sow-in) was a festival celebrating the end of the harvest season and the beginning of winter, the "darker half" of the year. During this time, from sunset on October 31st to sunset on November 1st, it was believed spirits would cross into our world. Therefore, offerings of food and drink were left outside for them. Additionally, when people left their houses after nightfall, they would go out in costume, to disguise themselves from the spirits.

Allhallowtide encompasses three days of remembrance of the dead, All Saints' Eve, All Saints' Day, and All Souls' Day (October 31 to November 2nd). During these days, Christians pray for the martyrs, saints, and all faithful departed Christians.

As Christianity spread to Celtic lands, the Church wanted to reconcile the differences between Christianity and Celtic beliefs to encourage the population to convert. Given the similarity in purpose and timing, it made sense. So the Samhain customs were adopted and Christianized, hence "Halloween", hallow from the Old English word for saint, and even or e'en from the word for eve.

As Halloween spread to North America, its celebration was initially limited and fragmented. It was not until the second half of the 19th century, when huge numbers of immigrants began to arrive, particularly from Ireland and Scotland, that Halloween began to be celebrated across the whole nation. It eventually transformed to be less focused on the superstitious and religious overtones, and more about children and family fun.

As it gained more popularity, Halloween was commercialized and taken worldwide. Halloween is a multi-billion dollar industry in the U.S., second only to Christmas. From the costumes, to the candy, to the haunted attractions, Halloween has something for everyone-and more history behind it than you think.