dressed as fairies, goblins, characters from their favorite movie franchise, and everything in between, partying and making mischief.

But outside of a good time, how many know why they do it?

Today, Halloween is a billion-dollar industry.

But exactly how did it get there?

[Haunting History: Halloween]

While today Halloween is synonymous with commercialism, it wasn't always that way.

The word "Halloween" comes from the words "hallow", meaning holy person, and "een", deriving as a contraction of eve.

And All Hallows' Eve finds its origins all the way back in the time of the ancient Celtic pagans with the holiday of Samhain, a three-day fire festival that essentially celebrated death and rebirth.

The Celts, who lived in what is now Ireland, Scotland, the UK, and parts of Northern Europe, based their calendar on the wheel of a year,

essentially divided into two halves: the light and the dark.

When one gave way to the other, this transition was marked by a fire festival.

The word "Samhain" translates into modern Irish to "summer's end".

Samhain celebrated the dead, and particularly, the celebratory feast paid homage to loved ones who had passed away recently.

Essentially as an invitation for their spirits to rejoin the living.

Many of Samhain's original rituals have been lost,

but what we do know of their holiday traditions from Celtic folklore and ancient Roman historians is that they were intended to connect them to spirits,

including costumes⏤most likely animal art first to help them hide from the unfriendly ones⏤feasting, and making lanterns from hollowed-out gourds,

seemingly the birth of the modern pumpkin Jack-o'-lantern.

Sacrifices generally of crops or animals were made during this time as an offering to the spirits.

It was popular for tricks or pranks to be played by humans and blamed on mischievous spirits.

As a result of the Roman invasion, with most of the Celtic land being conquered by Rome in 43 CE,

the spread of Christianity and Catholicism would force pagan Celtic traditions to evolve or be completely repressed.

In part, many Celtic traditions and popular pagan practices were reframed to fit within a Christian narrative as a way of converting people with greater comfort and ease.

Samhain would evolve into All Saints Day, which is also referred to as All Hallows Day, and was intended to be a day to celebrate the Christian saints and martyrs.

Essentially, instead of honoring pagan gods and mischievous spirits, they now celebrated Christian figures.

While the sacrifices were replaced by food offerings to the poor, the tricks and pranks continued.

But instead, they were now attributed to the spirits of the saints.

Halloween evolved as a more secular version of All Hallows' Eve,

and eventually, it would become more popular and common practice than All Saints Day.

While Halloween has its origins in the British Isles, there's a great disparity in its popularity in former British colonies.

The Puritans who came to colonize America were Protestant and did not celebrate holidays of the Catholic church, as they were believed to lead to idolatry.

In the early days of the American colonies, celebrations of Halloweens were mostly forbidden as they were deemed "too pagan" or "too Catholic" by the Protestant colonizers.

Though elements of it began to incorporate into secular harvest-related events in the 1800s.

The mid 19th century saw a large influx of immigrants entering the country, especially Irish immigrants who were greatly impacted by the potato famine.

With these people came Halloween customs out of which one of America's favorite holidays was formed.

In keeping with the mischief, children would dress in costumes and be given money or fruit for artistic offerings like poetry, songs, or even jokes instead of prayers.

By the late 19th century, children were playing seemingly innocuous pranks on their small local communities.

Adults would soon find incentive to dissuade children from playing pranks.

Enter trick-or-treating.

The 20th century would finally see the commercialization of Halloween.

By the 1920s and '30s, Halloween merchandise evolved to pre-made costumes for both children and adults.

After World War Two in the 1950s, the economic boom had candy manufacturers getting on the Halloween bandwagon.

Movies and TV are also largely responsible for the proliferation of Halloween as a mass-market holiday.

Cinemas in the '50s offered scary movie festivals.

And in the '60s, the new television industry began running Halloween specials during Halloween season.

By 2015, the National Retail Federation predicted spending on Halloween could reach $6.9 billion.

Whether you believe that we've lost the meaning or not, Halloween has since evolved far beyond the days of pagan fire festivals.

For more than a month out of the year, costume stores show up out of nowhere,

candy corn and Halloween-themed candies dominate whole aisles of grocery stores, and spooky shows and movies build out entire TV station schedules.

Whether you like it or not, whether you want to dress up as a gruesome goblin or a sexy cat, or ignore the holiday altogether,

Halloween has stood the test of time and proven itself as a holiday that's here to stay.