The article just kicks the can down the road: why is the left hand called the 'south paw' in boxing?
The real answer appears to be that "south" merely means "opposite" and "paw" means—of course—"hand".[1]
[1] http://www.wordorigins.org/index.php/site/comments/southpaw
Which is also why left handedness is so often literally translated to 'north-hand' in various Australian, South American and South African languages.