Southpaw came into vogue in 1885 thanks to Finley Peter Dunne aka Mr. Dooley, a famed Chicago sports journalist and humorist … and it had everything to do with the great all American pass time, baseball.
All major league baseball diamonds are laid out so the afternoon sun is to the batter’s back so he can see the ball coming at him from the pitcher’s mound. This means that the batter faces east.
Of course, since the batter is facing east, the pitcher must be facing west. Since science claims that 85% of people are right-handed, these leaves 15% of the population to be left-handed. And when a left-handed pitcher is on the mound, his throwing arm is, of course, facing south.
Since a left-handed pitcher pitches with his ‘south paw’ those who routinely use their left hand to write were soon referred to as ‘southpaws.’
While that incident certainly helped to popularize the word, the term south paw referring to a person’s left hand is attested as far back as 1848 in the slang of pugilism. A boxer who leads with the right hand and stands with the right foot forward, using the left hand for the most powerful blows was known as a southpaw almost 40 years before Finley Peter Dunne aka Mr. Dooley used the term.
Historically Speaking 