The word south pawgreenspun.com : LUSENET : Lefties : One Thread
Where does the word south paw originate from?
-- Kevin Milz (firstname.lastname@example.org), February 08, 1999
According to Partridge's Concise Dictionary of Slang and Unconventional English, edited by Paul Beale, published by Macmillan Publishing Company, NY, 1989 (based on A Dictionary of Slang and Unconventional English by Eric Partridge), one of the explanations for the term southpaw relates to baseball. On a regulation baseball field, the batter faces east (so the sun won't be in his eyes). This means that the pitcher faces west. For a left-handed pitcher facing west, his throwing/pitching arm (his left arm) would then be on the south side; hence, southpaw (paw = hand).
-- Michelle Hutchens (email@example.com), July 24, 1999.