The four-leaf clover is a rare variation of the common three-leaf clover. According to traditional sayings, such clovers bring good luck, though it is not clear when or how this idea began. The earliest mention of "Fower-leafed or purple grasse" is from 1640 and simply says that it was kept in gardens because it was "good for the purples in children or others".
Some folk traditions assign a different attribute to each leaf of a clover. The first leaf represents hope, the second stands
for faith, the third is for love and the fourth leaf brings luck to the finder.
Some reports claim six to be fame and seven to be longevity, though the notions' origination is unknown.
Others say that four-leaf clovers granted the power to see fairies, or that they are related to Saint Patrick's use of the shamrock to explain the Christian doctrine of the Holy Trinity to the Irish.
Four-leaf clovers commonly appear in centuries-old legends as symbols of good luck. The Druids (Celtic priests), in the early days of Ireland, believed that when they carried a three-leaf clover or shamrock, they could see evil spirits coming and have a chance to escape in time. Four-leaf clovers were Celtic charms, presumed to offer magical protection and ward off bad luck. Children in the Middle Ages believed if they carried a four-leaf clover, they would be able to see fairies, and the first literary reference to suggest their good fortune was made in 1620 by Sir John Melton.
Italian automobile maker Alfa Romeo used to paint a four-leaf clover, or quadrifoglio, on the side of their racing cars. This tradition started in the 1923 Targa Florio race, when driver Ugo Sivocci decorated his car with a green clover on a white background.
Los Angeles-based space exploration company SpaceX includes a four-leaf clover on each space mission embroidered patch as a good luck charm. Inclusion of the clover has become a regular icon on SpaceX's flight patches ever since the company's first successful Falcon 1 rocket launch in 2008, which was the first mission to feature a clover "for luck" on its patch.
Celtic Football Club, an association football team from Glasgow, Scotland, have used the four leaf clover as the club's official badge for over 40 years.