As tattoo designs and symbols, the shamrock and four-leaf clover are very popular with Celts of Irish descent. In fact it is hard to imagine a St. Patrick's Day without Shamrocks and Four-Leaf Clovers to accompany Leprechauns and green beer.
The Shamrock and Four-Leaf Clover are universal symbols of Ireland all over the world, a symbol of being of Irish descent and in the case of the four-leaf clover, a potent symbol of luck or good fortune. Interestingly enough, both shamrocks and four-leaf clovers are one in the same - with a crucial difference - and have a symbolic tradition that goes back many thousands of years, spanning both the periods of the Druids, the Celtic Tribes and the modern era of conversion to Christianity.
When St. Patrick traveled to the Ireland to convert the native peoples to Christianity, he used the local beliefs and the Shamrock leaf to illustrate the mystery of the Holy Trinity to the people of Ireland. St. Patrick taught that the one true God was divided into three: The Father, The Son and the Holy Spirit, when preaching Christianity to the Irish people - just as represented by the shamrock.
One of the reasons that a four-leaf clover is considered lucky is because of its extreme rarity. The odds of finding a Four-Leaf clover are estimated to be at least 10,000 to 1. The mystique of the four leaf clover continues today, since finding a real four leaf clover is still a very rare occurrence and an enduring omen of good luck.