Saint Patrick was not actually Irish. Historical sources report that he was born around 373 A.D. in either Scotland (near the town of Dumbarton) or in Roman Britain (the Romans left Britain in 410 A.D.). His real name is believed to be Maewyn Succat (he took on Patrick, or Patricus, after he became a priest). He was kidnapped at the age of 16 by pirates and sold into slavery in Ireland. During his 6-year captivity (he worked as a shepherd), he began to have religious visions, and found strength in his faith. He finally escaped (after voices in one of his visions told him where he could find a getaway ship) and went to France, where he became a priest (and later a bishop).

When he was about 60 years old, St. Patrick traveled to Ireland to spread the Christian word. It's said that Patrick had an unusually winning personality, and that helped him win converts. He used the shamrock, which resembles a three-leafed clover, as a metaphor to explain the concept of the Trinity (father, son, holy spirit).

Legend has it that Saint Patrick drove all the snakes out of Ireland -- that they all went into the sea and drowned. The snake was a revered pagan symbol, and perhaps this was a figurative tale alluding to the fact that he drove paganism out of Ireland.