Celtic dominance once extended across Ireland and much of Western Europe. It was the Druids (Celtic priests) who elevated four leaf clovers to the status of Celtic charms, allegedly potent against malevolent spirits. Their status as Celtic charms is the origin of the modern belief in their power to bestow good luck.

The leaves of four leaf clovers are sometimes said to stand for faith, hope, love, and luck. But another interpretation is widely known via the following verse:

I'm looking over a four-leaf clover
That I overlooked before.
One leaf is sunshine, the second is rain,
Third is the roses that grow in the lane.
No need explaining the one remaining
Is somebody I adore.
I'm looking over a four-leaf clover
That I overlooked before.

The first literary reference to draw on the tradition of four leaf clovers as Celtic charms seems to have been made in 1620. In that year, according to the University of Illinois, Sir John Melton wrote, "If a man walking in the fields find any four-leaved grass, he shall in a small while after find some good thing." On average, there are 10,000 three leaf clovers for every instance of a true four leaf clover.