Why do people celebrate St. Patrick's Day?
First, let's talk about why we're celebrating the man who was sort-of named St. Patrick. For instance: He's not a canonized saint by the Catholic Church, and his given name was Maewyn Succat, not Patrick. He did later take the name Patricius though. And he's also informally considered the patron saint of Ireland. He baptized thousands of Irish people and aided in the formation of hundreds of churches, so he was a huge force in bringing Christianity to Ireland, which has been a huge part of Irish identity ever since. You've probably also heard that he banished all the snakes. There were never any there to begin with, but that's still a nice story.
As to how that became the day we love/fear, March 17 is the day on which St. Patrick is thought to have died, and a Feast Day was instituted to commemorate his life and accomplishments. As Irish immigrants celebrated it across the pond in America in the early 18th Century, the feast became a bigger and bigger deal to the Irish community. This led to the first-ever St. Patrick's Day parade in Boston in 1737, and by 1903, the Feast Day was a national holiday back in Ireland.
Why do people wear green on St. Patrick's Day?
The link between green and Irish pride originated in the Irish Rebellion of 1798. As the Irish rebelled against the British soldiers, who wore red, they wore green uniforms. There's a famous ballad about this called "The Wearing of the Green," which is guaranteed to make you feel somber and proud even though you have no connection to those events. As a sign of solidarity with the rebellion, people began wearing green as an expression of Irish pride. Since St. Patrick's Day was the official day to express that pride, the two became linked. Originally, blue was the color most associated with Ireland, but the mix of national pride and green's association with the Catholic Church led to the green beer and green river we know the holiday by today.
Why do people pinch each other on St. Patrick's Day?
As you probably learned the hard way in middle school, those who don't wear green on St. Patrick's Day are eligible for pinches that range from flirtatious to malicious. One reason for this is that the holiday is about taking pride in one's Irish heritage, and the potential pinch encourages people to be bold about their Irishness. The second reason is leprechauns. The mischevious mythical creatures are rumored to pinch those aren't wearing green, but their non-existence makes it far more likely that you'll be pinched by an 11-year-old with a cruel streak.
Why do people drink on St. Patrick's Day?
As you know, folks who've so much as seen an Irish person on TV celebrate the holiday by drinking. This tradition has surprisingly innocent origins. During the original Feast Day-iteration of St. Paddy's, restrictions from Lent were cast aside and the day had a general atmosphere of indulgence -- that's the point of a feast after all. So, people ate and drank as much as their religiously observant hearts desired, though often this didn't involve beer. By law, pubs in Ireland had to shut down on the holiday for most of the 20th Century, and drinking on the holiday was generally considered a bad look until the late '70s. Then beer advertising made a big push to link drinking and the holiday for obvious reasons, and this marketing effort, along with some unfortunate stereotypes, are the reason you'll either be in hiding on Saturday or having a very un-festive Sunday.
So, whether you're drinking Guinness, Jameson, or tea this St. Patrick's day, pour one out for Maewyn Succat.