Shamrock (How It Came To Be The National Emblem Of Ireland). According to tradition, when Saint Patrick landed near Wicklow, to convert the Irish, in 433, the pagan inhabitants were about to stone him; hut having obtained a hearing, he endeavoured to explain to them the Trinity in Unity; but they could not understand him till, plucking a shamrock - three-leaved grass, or trefoil - from the ground, he said, "Is it not as possible for the Father, Son, and Holy Ghost, as for three leaves to grow upon a single stalk " Upon which, says the legend, the Irish were immediately convinced.