St. Patrick's Day is the day that St. Patrick died. St. Patrick is a global celebration that is on March 17th. The name St. Patrick was originated from a Irish man called St. Patrick he was one of Ireland patron saints who ministered Christianity in Ireland during the fifth century.
St. Patrick was actually British he was born by roman parents in Scotland or wales in the late fourth century he used the shamrock as a metaphor for the holy trinity when he was first introducing Christianity to Ireland. if you did not wear green it was considered shameful so you get pinched.