"Wearin' o' the green"
The shamrock became symbolic in other ways as time went on. In the 19th century it became a symbol of rebellion, and anyone wearing it risked death by hanging. It was this period that spawned the phrase "the wearin' o' the green". Today, the shamrock is the most recognized symbol of the Irish, especially on St. Patrick's Day, when all over the world, everyone is Irish for a day!
The original Irish shamrock (traditionally spelled seamróg, which means "summer plant") is said by many authorities to be none other than white clover (Trifolium repens), a common lawn weed originally native to Ireland. It is a vigorous, rhizomatous, stem-rooting perennial with trifoliate leaves. Occasionally, a fourth leaflet will appear, making a "four-leaf clover," said to bring good luck to the person who discovers it.