Ok, so every year it seems my social media is bombarded with angry Pagans decrying the celebration of St. Patrick's Day because he is being celebrated for driving all the Snakes out of Ireland... and "snakes" means "pagans": WRONG!!!
Seriously, it's bullsh*t, stop repeating it.
Firstly St Patrick did not rock up in Ireland to drive out Paganism and replace it with Christianity. There were already Christians in Ireland when he got there, quite a lot of them. There is a whole host of historical figures that were associated with spreading Christianity in Ireland, from Finnian of Clonard, who trained The Twelve Apostles of Ireland, through Palladius and then onto the subject of this article himself.
The misconceptions about St. Patrick aren't contained to the Pagan community, even the church themselves are thought to have fudged the dates placing Patrick in Ireland 30 years earlier than he actually arrived. This is believed to be because they grew to prefer him as a figure to Palladius, and it allowed them pass credit for a lot of the work Palladius did to Patrick.
It is believed Palladius was sent to Ireland to stop Pelagianism - (a believe system within Christianity that believes people can earn salvation by their own efforts, rather than just by the grace of God) - from establishing among the Christian community.
Secondly snakes were much more commonly associated with the Devil or evil, than they were with Pagainism. They could have been used as a symbol of many things, from original sin through to the afore mentioned Phelagians (the theory I favor).
So when you see cartoons of St. Patrick driving snakes out of Irelands, what you're actually seeing is Palladius stopping Pelagians entering Ireland... or at least keeping them quiet when they got there.
St. Patrick was born in Roman Britian, and despite having a Decon for a father and a priest for a grandfather, he didn't find faith himself until he was kidnapped by Irish pirates at 16 and lived as a slave for 6 years. Upon escaping he returned to England and continued to study Christianity, eventually returning to Ireland as a missionary.