Where did the phrase "south paw" for left handed people originate from?

Answer 1

It was originally a term for a left handed baseball pitcher. Most baseball diamonds were built so that the pitchers left arm was to the south when on the mound. This orientation kept the sun from being in a hitters eyes.

Answer 2

According to the "New Dickson's Baseball Dictionary," the term was coined in the late 1800s to describe left-handed pitchers, who, facing west in most ballparks, had their left arms hanging on the south side of the ballpark. A sportswriter, Harry Grayson, investigated this theory in 1951, and determined that most ballparks in fact placed home plate on the west side of the diamond, on the principle that this would keep the sun out of hitters' eyes during day games. The term has been applied to other sports, including boxing, and obviously came into general use. The term "northpaw" never caught on, though.