Common misconception. In truth, Saint Patrick was drunk beyond the levels normally attainable by even the Irish. Stumbling around his village, he saw a patch of clovers growing near the village tavern. He roughly grabbed a handful and yanked them from the ground, using his free hand to grab a random villager by the collar, yank them close enough for the person to smell the alcohol and boiled sheep intestine on his breath, and exclaim "You! Look! TINY LEAVES." He shook the person violently, punched them in the face, then proceeded to run into the tavern, throwing clovers everywhere while shouting "TINY LEAVES." Everyone was in awe of the level of inebriation he had reached, and insisted that such a feat deserved a holiday.
I have no idea how he became a saint. Something about snakes or some shit. I dunno, I was drunk when I heard the story.