The three portrusions may also be symbolic of the three theological virtues found in first Corinthians 13:13: Faith, Love, Hope
The Irish have considered shamrocks as good-luck symbols, and today people of many other nationalities also believe they bring good luck. Sometimes shamrocks can be found with four leaves. These are rare and considered to be very lucky for the finder.
And here are some of my mug cozies with shamrock from my shop - Lilac Gifts - for all the deatails and prices click HERE