Get out your green on Thursday: It's St. Patrick's Day! And just incase you want to sound extra smart at an upcoming party, here are 8 fun factoids you may not already know about the annual holiday:

1. St. Patrick was not actually Irish:

Patrick was a nobleman born in about 400 A.D. in Britain and kidnapped by Irish pirates at the age of 16, said Philip Freeman, author of St. Patrick of Ireland: A Biography.

Patrick was born into a religious family, but was an atheist early in his life. However, he rediscovered his faith while enslaved in Ireland. After 17 years as a slave, St. Patrick escaped Ireland and found his way home, but returned to Ireland as a missionary, according to Freeman.

"He said he was ready to die in Ireland in order to make his mission successful," Freeman said.

It's unclear if St. Patrick did in fact die in Ireland, but March 17 is widely believed to be the day of his death.

A stained glass window of St. Patrick at the St. Thomas Aquinas Church in Brooklyn, N.Y.  
A stained glass window of St. Patrick at the St. Thomas Aquinas Church in Brooklyn, N.Y.  

2. Prolific parties and parades:

St. Patrick's Day began as a religious holiday in Ireland but became a celebratory affair because of Irish Americans, according to Timothy Meagher, a history professor at Catholic University in D.C.

In the United States, St. Patrick's Day was first celebrated with banquets at elite clubs in Boston, Philadelphia, New York, Charleston, S.C., and Savannah, Ga., Meagher said.

Then, the celebrations expanded into parades. New York City hosted the first St. Patrick's Day parade in 1762, and by the mid-19th century parades were common, he said.

"The parades are a statement of showing our colors, showing our numbers, showing that we are powerful and important," Meagher said of the role of parades in celebrating Irish-American identity.

The shortest St. Patrick's Day parade in America is said to be in Hot Springs, Ark., where marchers dressed in green go 98 feet before calling it quits.

According to statistics compiled by WalletHub, $4.4 billion will be spent on St. Patrick's Day events and memorabilia this year, with each person doling out an average of $35.40.

3. Green River in Chicago a family affair:

Another unique tradition that has grown in popularity every year is the annual dyeing of the Chicago River for St. Patrick's Day.

If you've never had the chance to see it, you can watch a timelapse here:

The Butler and Rowan family clans are responsible for turning the murky water bright green, and they've done it for more than 50 years.

The only way to become part of the six-person boat crew is to be related by blood or marriage to either Mike Butler or Tom Rowan, according to The Chicago Tribune. Each year, the crew shakes an orange powder — a top secret recipe — into the Chicago River from a sifter and it stays green for about five hours.

4. Gobs and gobs of Guinness:

The Irish stout is the drink of choice on St. Patrick's Day.

On a typical day, Americans drink about 600,000 pints of the Dublin-based beer. But on St. Patrick's Day, about 3 million pints of Guinness are downed, according to Guinness in an email to USA TODAY Network.

Planning on drinking a pint on Monday? Tips from Guinness on the perfect pour: Tilt the glass at 45 degrees when pouring until it is three-quarters full, then let the beer settle before filling the glass completely to the top.

Analysts are predicting that 13 million pints of Guinness will be consumed worldwide, during this year's holiday.

5. Shamrocks 'drowned' in spirits:

Legend has it that St. Patrick used the three-leaved shamrock to explain the Christian Holy Trinity.

But Freeman said, "There's no evidence St. Patrick ever did that."

Traditions as early as the 17th century incorporated the plant, said Mike Cronin, author of Wearing the Green: A History of St. Patrick's Day.

People wore shamrocks on their coats and closed the day by "drowning the shamrock" — placing it in a glass of whiskey before drinking, Cronin said.

Every year, the president of Ireland sends the U.S. president a crystal bowl filled with shamrocks, in honor of the holiday.

Jozee Killoren of Hartford, Wis., looks through her shamrock glasses before the start of the Shamrock Shuffle 5K Race/Walk in Hartford on March 16, 2013.
Jozee Killoren of Hartford, Wis., looks through her shamrock glasses before the start of the Shamrock Shuffle 5K Race/Walk in Hartford on March 16, 2013.

6. Lucky leprechauns:

Today's leprechauns, usually rosy-cheeked, boozy little men in green attire, come from Irish folklore. And in case you're wondering, the current market value of a leprechaun's pot of gold (which contains 1,000 gold coins, weighing an ounce each) is $1.2 million, according to WalletHub.

The first recorded mention of a leprechaun goes back to the 8th century, coming from the word luchorpán, meaning "little body" to describe water spirits, according to John and Caitlin Matthews in The Element Encyclopedia of Magical Creatures.

Another possible origin is the Irish god Lugh, whose Welch variant is known as one of the "Three Golden Shoemakers."

There's also the Irish fairy Cluricaune, "a cunning spirit who haunts cellars, drinks, smokes and plays tricks," the Matthewses write. Cluricaune was popularized in a 1825 publication called Fairy Legends.

7. So much corned beef and cabbage:

Although a classic St. Patrick's Day meal, corned beef and cabbage is more American than Irish.

Irish Americans in the 19th century were mostly poor. The most affordable meat available was corned beef, according to Cronin.

And cabbage? "It's a spring vegetable and it's cheap," Cronin said.

Industry experts say cabbage shipments increase 70 percent during St. Patrick's week, according to WalletHub.

8. Irish Americans:

While lots and lots of people like to celebrate the holiday in the U.S., 33.1 million is the official number of U.S. residents who currently claim Irish ancestry, according to WalletHub.com. That calculates to seven times the entire population of Ireland.

Broken down state-by-state, 10-15 percent of people who live in Oregon say they are Irish.