NEVER SAY HAPPY SAINT PATTY: " Saint Patrick's Day: Why 'Paddy' is fine – but never 'Patty' | Europe | News | The Independent

"...
As Marcus Campbell, the one-man crusade behind
the ' Paddy not Patty' website and the Twitter feed of
the same name, says: "There isn't a sinner in Ireland
that would refer to a Patrick as "Patty". It's as simple
as that."..."

http://www.independent.co.uk/news/world/europe/st-patricks-day-2016-saint-paddy-patty-a6936506.html