St Patrick’s Day is never Patty’s Day. Who even is Patty?

Let’s get the obvious out of the way; it’s called St Patrick’s Day. Paddy’s Day is also acceptable. What it is never called is, Patty’s Day. Never.
Who even is Patty? The first image that springs to mind is the chain-smoking sister of Selma from The Simpsons. Certainly not the same person who was a fifth-century Romano-British Christian missionary and bishop in Ireland. Nor the same individual who became essentially one of our first known influencers due to his popularisation of Shamrock or his ‘alleged’ banishing of the snakes from our fair isle by chasing them into the sea after they attacked him during a 40-day fast he was undertaking at the top of a hill.