MEANING: Trinity Knot was adapted by early Christians as a symbol of the Father, Son and Holy Ghost. The three-leafed shamrock is mainly an Irish Christian symbol of the Holy Trinity. Legend has it, St. Patrick used the shamrock to illustrate the Doctrine of the Trinity. When you look at the Shamrock there is the stem and then three leaves. God is the stem and then on each of the leaves is the Father, the Son and the Holy Spirit.