Paddy cake, Paddy cake, pour me a Guinness...

This in from Grammar Girl:

Each year, millions of Americans annoy the Irish by referring to St. Patrick's Day as St. Patty's Day. For the record, the correct short form is St. Paddy's Day. According to the Provisional Government of Paddy, not Patty, the d's in Paddy come from the Irish spelling, Pádraig.

And yes aye, over at paddynotpatty.com, they spell it out for you. Literally.

Each and every year millions of Irish, Irish-ish and amateur alcoholics are needlessly distracted from their Holy Tradition of drinking themselves into a stupor in the name of Saint Patrick, a Roman Briton slave holding the dubious honour of bringing Christianity to an island that would use it as another convenient excuse to blatter the hell out of each other for centuries.

The source of this terrible distraction?

An onslaught of half-hearted, dyed-green references to St. Patrick’s Day as St. Patty’s Day.

It gnaws at them. It riles them up. It makes them want to fight… you know, more than usual.

IT'S PADDY, NOT PATTY. EVER.

SAINT PATRICK’S DAY? GRAND.

PADDY’S DAY? SURE, DEAD-ON.

ST. PAT’S? AYE, IF YE MUST.

ST. PATTY? NO, YE GOAT!

Paddy is derived from the Irish, Pádraig, hence those mysterious, emerald double-Ds.

Patty is the diminutive of Patricia, or a burger, and just not something you call a fella.

There is not a sinner in Ireland that would refer to a Patrick as “Patty”. It’s as simple as that.

Also, shamrocks have THREE leaves and are not "four leaf clovers." Saint Patrick used them to illustrate the Trinity. Clearly, I've had it wrong all this time too. Also noted at paddynotpatty.com, "shamrock shakes" are vile, and any drink called an "Irish car bomb" is in incredibly offensive.

Agreed. And any douchebag trying to market a "burning twin towers" cocktail after Nine Eleven should be bitch slapped too.