St Patrick’s Day is an Irish cultural and religious holiday, named after the patron saint of Ireland. Patrick was born in Roman Britain, but as a teenager, he was captured by Irish pirates and whisked away to Ireland. He stayed there as a slave for six years, but finally escaped back to Britain. Later he returned to Ireland, as a missionary, trying to convert the Celts to Christianity.
If you want to celebrate St Patricks Day, you could wear the symbols of Ireland : the shamrock and the colour green.
How about a green shamrock scarf?