In sports, particularly in baseball or boxing, the term southpaw refers to someone who is a left hander. I have always known this, at least since I've been a sports fan (32 years now), but I have not known until today where this term comes from.
In the early days of the sport, baseball parks were built facing the east. So neither the batter nor the hitter would have the sun in their eyes. This meant that right hander pitchers faced the north during their wind-up. Lefties ... of course, they faced the south.