I found this online at Time.com; I thought it was interesting. It may be old news to some, but maybe not for others? Anyway....
The True History Behind St. Patrick's Day
By: Ashley Ross
Mar 16, 2016
The modern St. Patrick's Day celebrations that will take place on Thursday, at least in the United States, will likely be characterized by commercial lucky charms and green beer—all of which has very little to do with the historical figure of the saint. As it turns out, it took centuries for the holiday to accrue the elements that now seem crucial to its celebrations.
The March 17 celebration started in 1631 when the Church established a Feast Day honoring St. Patrick. He had been Patron Saint of Ireland who had died around the fifth century—a whopping 12 centuries before the modern version of the holiday was first observed. But very little is known about who he actually was, according to Marion Casey, a clinical assistant professor of Irish Studies at New York University (and a regular marcher in the St. Patrick’s Day Parade in Manhattan).
“We know that he was a Roman citizen, because Britain was Roman then, and then he was enslaved and taken to Ireland, where he either escaped or was released,” Casey says. “And then he became a priest and went back to Ireland, where he had a lot of luck converting the Druid culture into Christians.”
Legend says St. Patrick was actually born Maewyn Succat, but that he changed his name to Patricius (or Patrick), which derives from the Latin term for "father figure," after he became a priest. And that supposed luck of his is the root of all the themed merchandise for modern St. Patrick’s Day.
It wasn’t until the early 18th century that many of today’s traditions were kicked into high gear. Since the holiday falls during Lent, it provides Christians a day off from the prescriptions of abstinence leading up to Easter, and around the 1720s, the church found it “got kind of out of control,” Casey says. It was to remind celebrants what the holiday actually stood for that the church first associated a botanical item—customary for all saints—with St. Patrick, assigning him the symbol of the likewise lucky shamrock.
Modern-day celebrations and themes continued to take shape during the rest of the 1700s. In 1762, the first New York City parade took place. It wasn’t until 1798, the year of the Irish Rebellion, that the color green became officially associated with the day, Casey says. Up until the rebellion, the color associated with St. Patrick was blue, as it was featured both in the royal court and on ancient Irish flags. But as the British wore red, the Irish chose to wear green, and they sang the song “The Wearing of the Green” during the rebellion, cementing the color’s relevance in Irish history.
As for the green beer, that's an even later addition. In fact, it wasn't until the late 20th century that Ireland repealed a law that initially kept everything—pubs included—shut down for the day. Since then, thanks to a marketing push from Budweiser in the 1980s, downing beer has become a common way to celebrate, regardless of how closely it’s tied to the actually meaning of St. Patrick himself.