1.  The shamrock, a three-leaf clover, was called the “seamroy” by the Celts and was considered a sacred plant that symbolized the arrival of spring.  St. Patrick used it as a way of explaining the doctrine of the Holy Trinity.

2.  In Celtic folktales, leprechauns were cranky souls, responsible for mending the shoes of the other fairies.

3.  The staple St. Patrick’s Day meal . . . corned beef and cabbage . . . was an American innovation.  Ham and cabbage were eaten in Ireland, but corned beef offered a cheaper substitute for poor immigrants.

4.  The Toronto Maple Leafs hockey team was known as the Toronto St. Patricks from 1919 to 1927, and they wore green jerseys.  On St. Patrick’s Day in 1999, the Maple Leafs took the ice in green St Patricks throwback uniforms.

Here is today’s bonus fact:

5.  It’s believed that if you wear green then you will be invisible to leprechauns.  If you aren’t wearing green, then a leprechaun will see you and pinch you.  That’s the basis behind the tradition of pinching people who are not wearing green.

(History / MythEncyclopedia / Smithsonian / Wikipedia / SFist)