Since the operative number here is four, the history behind four leaf clovers as lucky charms is clearly distinct from the Trinitarian tradition behind the shamrock. Indeed, the significance invested in four-leaf clovers pre-dates Christianity, going back to the pagan period, when four leaf clovers were Celtic charms. 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.

Shamrock is now used as the emblem of Ireland and an unofficial symbol of Ireland and Boston, Massachusetts.

In fact, St. Patrick's Day parades are an American invention. The first parade honoring the day occurred in Boston in 1762. Over the years, parades and other celebrations on St. Patrick's Day became a way for Irish immigrants to remember their roots.

There are some historic cases linked with the four-leaf clovers. Abraham Lincoln, the late US President was said to carry a four-leaf clover everyday with him, except on the day he was assassinated. Napoleon Bonaparte, the late French emperor, escaped assassination when a bullet whisked past his head. At that moment, he was stooping down to pick up a four-leaf clover.

The Druids believed that a four-leaf clover could help in spotting witches or other demons. Some modern-day spiritualists claim that a four-leaf clover releases energy and helps one's judgment. Yet others feel that finding a four-leaf clover brings good fortune, not just on St. Patrick's Day.  Normally, the clover plant produces the familiar "segmented" leaf with three parts. However, botanists believe that if a young clover leaf is damaged or exposed to certain chemicals, then it produces a four-leaf clover.

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.

According to Nathaniel Colgan, the botanist and author of The Flora Of County Dublin in 1904, people even ate the shamrock in times of famine.

In the 19th century it became a symbol of rebellion against the English and began to be strongly associated with Irish identity. Apparently anyone wearing it risked death by hanging.

The shamrock was an important plant to the Druids (Celtic priests or polytheists who believe in worshiping of multiple gods or deities) prior to Saint Patrick. It was believed to have medicinal properties and its association with the number three had significant meaning in ancient numerology, in which three was a sacred number with mystical powers.

It has been said that St. Patrick killed all of snakes in Ireland. Some believed that people worshipped St. Patrick because he survived from numerous snakes' bites. That's because people thought that he was God. But they were all myths. Snakes, in fact, symbolized pagen's gods and evil spirits in Ireland. There were no snakes in Ireland due to the unfriendly weather.

The shamrock might even have been thought to have prophetic properties, as some say an upward direction of its leaves foretold grave weather. The Druids also believed the shamrock could ward off evil spirits.