In the United States, wearing green on St. Patrick's day pays tribute to the Emerald Isle, (Ireland) and it’s good people but also so you don’t get pinched. That’s right. Pinched! If you forget or choose not to wear green on St. Patrick’s day, your friends have the right to pinch you for not wearing green. Usually the pinching occurs on the back side but other area's of the body is acceptable as well.
There you have it, the reason for Wearin O The Green.