The term "shamrock" derives from the Irish word, seamrog, which translates to "little clover." However, there is no one plant, unique to Ireland, which alone bears the name shamrock. A survey conducted at the National Botanic Gardens in Dublin revealed that what Irish folk consider shamrock can be one of four common clovers or trefoils.

According to Irish legend, the druids in Ireland looked at the shamrock as a sacred plant because its leaves formed a triad. Three was a mystical number in the Celtic religion.

Later, St. Patrick used the shamrock in the 5th century to teach Christianity by explaining that each of the three leaves illustrated the Father, the Son and the Holy Spirit of the Holy Trinity.

In the 19th century the shamrock became a symbol of rebellion against the English and began to be strongly associated with the Irish people.