It is never too early to issue a warning. St. Patrick's Day will be upon us in a few weeks, and, while people are still reasonably sober they may heed this caution.
The diminutive of the saint's name is Paddy; it derives from the Irish version of his name, Padraig. Many people on these shores mistakenly refer to St. Patty's Day, but Patty is the diminutive of Patricia. If you want to be on familiar terms, and not identify yourself publicly as a daft eejit, speak or write of St. Paddy's Day.
I issued this reminder last year, referring people to the Paddy Not Patty website, and many of the comments, here and there, challenged these simple facts in a tone that was belligerent and, frankly, moronic.
You can do better.