A shamrock painted on a window in New York City for St. Patrick’s Day 2005. (Photo by Spencer Platt/Getty Images)

One of the symbols associated with St. Patrick’s Day is the shamrock. It’s seen everywhere on the holiday, which honors the Patron Saint of Ireland and Irish culture. It’s believed that St. Patrick used the three-leaf shamrock to represent the Holy Trinity.

The work “shamrock” describes a young clover. So, all shamrocks are clovers, but not all clovers are shamrocks.

As for the four-leaf clover, it doesn’t have anything to do with St. Patrick’s Day. The four-leaf clover represents good luck, but it wouldn’t have helped St. Patrick explain what the Holy Trinity is.

Here is what you need to know about the shamrock.

1. St. Patrick Used the 3-Leaf Clover to Represent the Holy Trinity

St. Patrick's Day 2017, Shamrock, Shamrock facts, Shamrock meaning

An Aer Lingus jet. (Getty)

There’s a very specific reason why the three-leaf clover is associated with St. Patrick’s Day instead of the lucky four-leaf clover. It’s believed that St. Patrick used the shamrock to help explain the Holy Trinity to the Irish when he arrived there in 432 A.D.

According to Catholic Hot Dish, there are several different legends about how St. Patrick used the shamrock. In one, he used it in a sermon to explain it directly to King Laoghaire. In another, he saw a group of Irish chieftains in a meadow. He picked up a shamrock to explain the Holy Trinity.

St. Patrick showed that the three leaves represented the Father, the Son and the Spirit, but these leaves were part of one plant, or one God.

As for St. Patrick himself, he was born in Great Britain and has been venerated in the Catholic Church, Eastern Catholic Churches, Eastern Orthodox Church, Anglicanism and Lutheranism. It’s believed that he lived during the second half of the 5th Century. March 17 is the supposed date of his death.

Catholic.org estimates that he was born in 387 and died in 461, meaning that he would have lived to be 74 years old.

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2. The Odds of Finding a 4-Leaf Clover Are 1 in 10,000

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President Donald Trump accepts a bowl of shamrocks from Irish Prime Minister Enda Kenny on March 16, 2017. (Getty)

As Inside Science notes, scientists are still trying to figure out how four-leaf clovers happen. They are rare, as it is estimated that thee are only 1 in 10,000 plants that grow four leafs. Scientists are trying to determine if it has to do with genetics or the environment.

In 2010, there was a study published in Crop Science, by University of Georgia researcher Wayne Parrott. He said his lab found where the gene that creates the trait is, but couldn’t identify what the gene was. “You know it’s inside this locked trunk and we don’t have the key to open it,” he told Inside Science in 2017. But Parrott’s research also showed that the environment where a plant is grown can also play a role.

Parrott told Live Science that his real goal is to get more people interested in using white clovers as decoration because it’s better at keeping soil fertile for other crops and plants.

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3. The Word ‘Shamrock’ First Appeared in English Literature in 1571

The word “shamrock” comes from the Irish word “seamair óg,” which means “young clover.” The word didn’t show up in English literature until 1571, when it appeared in Edmund Champion’s Boke of the Histories of Irelande.

In the book, Champion wrote that he saw Irish eat “shamrotes, water-cresses, roote, and other herbes.” He added that they “cramme together” oatmeal and butter and drink “whey, milke and beefe broth.”

Several other works throughout the 16th and 17th centuries claim that the Irish are shamrocks and by then, it was closely associated with the Irish for many English writers. But this was likely because English writers were confused by the word “seamsóg,” which means “wood sorrel.” The writers might have not realized that the shamrock was a clover.

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4. Ireland Began Adopting the Shamrock as a National Symbol in the 1700s

By the 18th century, the Irish began using the shamrock as a national symbol, as it outgrew its association with just St. Patrick. In 1800, when the Kingdoms of Great Britain and Ireland were united, the shamrock was added to the Royal Coat of Arms. As Northern Ireland is still part of the U.K., a sharmock and the Harp of Ireland remain on the Coat of Arms.

The shamrock is the national flower of Ireland and is used as a symbol throughout the government. It’s even part of Aer Lingus’ logo and its traffic control call sign is Shamrock.

Still, the harp is the real national symbol of Ireland and is featured in the country’s coat of arms.

When Irish Prime Minister Enda Kenny visited the White House on March 16, he presented Trump with a bowl of shamrocks, as Irish leaders have done so in the past when first meeting their American counterparts.

After meeting with Trump, Kenny told RTE.ie that their conversation focused on immigration. Trump told Kenny that he wants to go to Ireland during his first term in office.

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5. Blue Was Originally the Color of St. Patrick

As many historians will remind people on St. Patrick’s Day, the original color associated with St. Patrick was blue. According to Time Magazine, St. Patrick’s Blue was used on ancient Irish flags. The Irish Coat of Arms also has the harp on a blue field and earlier versions used a lighter shade of blue.

During the 1798 Irish Rebellion, the clover became a national symbol and that’s how green became associated with Ireland and, ultimately, St. Patrick’s Day.

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