Associated Press

You may already have purchased candy and put out decorations, but how much do you know about Halloween? From Halloween's origins to the most-popular costumes of the year, this list will provide the last bit of information you need to feel prepared for Oct. 31.

Halloween is a contraction of All Hallows' Eve
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The word "Halloween" is believed to have originated about 1745. It comes from the Scottish, "All Hallows' Eve." The term "All Hallows' Eve" itself is believed to have originated in the 16th century.

Americans spend over $2 billion on Halloween candy

According to the National Retail Federation, the average person will spend about $77 on candy for Halloween in 2014. When divided, that means Americans will spend over $2.2 billion on candy this Halloween.

Top adult costumes
Associated Press

The top four costumes for adults:
1) Witch
2) Animal
3) Batman character
4) Pirate

Source: National Retail Federation

Halloween is the start of the triduum of Hallowmass
Associated Press

Halloween represents the start of a three-day period of remembrance of saints, martyrs and the faithful who have died in Western Christian society.

The days of celebration are All Hallows' Eve (Halloween), All Saints' Day and All Souls' Day.

Halloween is heavily influenced by Celtic culture
Associated Press

Before Christianity showed up on the shores of the British Isles, the local Celts celebrated the end of summer and the harvest with the festival of Samhain. During this time, it was believed that the spirits and fairies were more active in the mortal world. Offerings of food were given to the spirits to ensure they didn't wreak harm on the village people, and great bonfires were lighted for their protective and soul-cleansing powers.

When Christianity came to Britain and eventually supplanted paganism as the dominant religion, Celtic culture still found ways to influence it. It's similar to how the Day of the Dead in Mexico is heavily influenced by pre-existing native culture.

Top chocolate brands
Associated Press

The three top chocolate brands in 2013 were Snickers, M&M's and Reese's Peanut Butter Cups, according to Business 2 Community.

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Souling, guising, mumming, all are terms for going door-to-door asking for offerings. But it wasn't until 1927 that the term "trick-or-treat" was first used, originating in a newspaper report from Blackie, Alberta, in 1927.

"Trick" is the threat if no "treat" is given. Today trick-or-treating is one of the most visible celebrations of halloween, with many different variations of it being practiced all over the world.

All Saints' Day was moved from May to November as part of the Celtic festival

Established in either A.D. 609 or 610, All Saints' Day, the Christian day for remembering the dead, was celebrated on May 13.

However, in the 8th century, Christianity started branching out and attempted to mesh with the various pagan cultures of its followers, rather than completely supplant them. To this end, All Saints' Day was officially moved to Nov. 1 in A.D. 835 and used the traditional pagan festivities on Oct. 31 to mark the beginning of a Christian holiday.

Top children's costumes
Associated Press

The top five costumes for children:
1) Disney's Frozen characters
2) Teenage Mutant Ninja Turtles
3) Princess
4) Animal
5) Spider-Man

Source: National Retail Federation

Soul cakes were the origin of trick-or-treating
Associated Press

Before people handed out candy, there was "souling," the act of groups of people (mainly children) going around and collecting "soul cakes" in exchange for reciting prayers and songs on behalf of the dead and departed.

Parents eat the candy, too

About 90 percent of parents admit to eating some of their child's trick-or-treating spoils, according to Lois Collins.

Dressing up in a costume was a matter of life or death
Associated Press

It was believed that restless spirits would roam the earth until All Saints' Day, which meant that All Hallows' Eve was their last chance to exact revenge on the living for past grievances and slights. And so people would dress up to disguise themselves from these spirits. Poor churches would also dress priests up as martyrs and saints instead of building expensive statues of them for the celebration.

Turnips were the original pumpkins

Pumpkins are native to the New World, so before Christopher Columbus sailed the ocean blue, celebrators of All Hallows' Eve had to carve their jack-o'-lanters out of turnips.

The Jack in jack-o’-lantern is a person
Associated Press

It was a former person to be precise. According to one Irish folklore story, a crafty man named Jack tricked the devil into climbing a tree and then carving a cross on the tree, trapping the devil. Jack let the devil go, but not before getting assurance that the devil would never collect Jack's soul. The devil agreed, and Jack went on to live a sinful life.

Upon death, Jack was promptly turned away from heaven. True to his word, the devil didn't let Jack into hell either, instead throwing a fiery piece of coal from the pit of hell at him, which Jack caught and put into a carved out turnip. He then wandered the earth without anywhere to go.

The actual tradition of putting lights inside carved out objects is actually just a continuation of lighting the way for the spirits that were believed to rise from the grave and visit their families once more, but where's the fun in that?

Top pet costumes
Associated Press

The top five costumes for pets:
1) Pumpkin
2) Hot dog
3) Devil
4) Bumble bee
5) Cat

Source: National Retail Federation