As history tells it, St. Patrick utilized the three leafed clover as an illustration of the Christian holy trinity. St. Patrick visualized the the three "hearts" on the clover that was so prevalent on the Irish hillsides, the shamrock seemed a perfect visual-aid for making his point. St. Patrick was passionate about sharing his faith with the people of Ireland, and associated each leaf of the clover with the Holy Trinity (Father, Son, & Holy Spirit).
I like Patrick's style. Also, I love that the shape of each shamrock leaf is a heart. Happy St. Patrick's Day!