St. Patrick’s Day is celebrated worldwide on the 17th of March every year. It honors the catholic saint, St. Patrick, who was known to get rid of the Ireland snakes in the 5th century. According to the legend, he chased the snakes into the sea of water after they began attacking him during his 40 day fast he underwent on a hill.
Scholars have suggested over the years that the snakes were not real snakes, and in fact where a metaphor for the symbols of evil in the religion of Christianity. For example, the bible portrays a serpent as the one who tempted Adam and Eve.
Therefore making the legend true in some ways because to many the snakes symbolized evil and back then evil was seen as those who went against the Christian religion, making them snakes. Ultimately the legend came from the truth of St. Patrick pushing out all the pagans by enforcing the christian religion on the entire country, leaving pagans no choice but to leave.