What does the name Horgan mean?

The name Horgan means 'Champion', the gaelic version is O'hArgaín. There is a town called Ballyhorgan in the region of Munster in the Republic of Ireland, and, in the region of Munster the name is most commonly found, specifically in the counties of Kerry and Cork. Interestingly, it is not uncommon to find the Horgan name in Portugal. If anybody knows why that is, I'd be keen to know.