The way I heard it, from an old 50s folkie named Jimmy Gavin (anyone remember him)?

Now here's to good St. Patrick who by strategy and stealth
Drove all the saints from Ireland, here's a bumper to his health
But not too many bumpers, or we'll lose our heads and then
We'll forget the good St. Patrick, and see the snakes again

Now Ireland was Ireland when England was a pup
And Ireland will be Ireland, we'll lick those muckers up,
I'm a good old Roman Catholic, I go to church each Mass,
But ye lousy British Protestants can kiss me Irish ass.