Green’s Dictionary of Slang

1. left-handed.

1903		Eve. World (NY) 6 Feb. 10/6: Dr S. Timm, the southpaw crack of the Fdelias.
1908		N.Y. Globe 21 Apr. in Fleming Unforgettable Season (1981) 45: The Giants are weaklings before left-handers [...] Covaleski, Pastorius, Rucker – three southpaw victims.
1915		S. Ford Torchy, Private Sec. 40: They’re thinkin’ of puttin’ in left-handed straps for south-paw passengers.
1924		C.S. Montanye ‘The Dizzy Dumb-Bell’ in Top Notch 1 Aug. 🌐 Perry, turning southpaw against a left-handed batter, blanked him.
1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 60: It was swell for Studs to play [...] and pick one of Helen’s southpaw kicks out of the air.
1940		Dundee Courier 24 Feb. 7/6: Richardson found the ‘south-paw’ stance of the Englishman an awkward proposition.
1950		Chicago Daily News 18 Mar. 11/4: Bob Henry, a 19-year-old south paw pitcher from the University of Texas, has been signed by the Chicago Cubs [DA].
1998		P. Luff ‘Left-handed Children’ on UK Parliament Commons 22 Jul. 🌐 According to The Economist, researchers preparing a survey of English dialects found 88 different words for left-handed in local use in the 1950s. Such words include buck-fisted, cack-handed, caggy, clicky, corrie-pawed, cow-pawed, cuddy-wifter, dolly-pawed, gar-pawed, gibble-fisted, golly-handed, keck-fisted, keggy-handed, left-plug, left-kelly, scoochy, scrammy-handed, skiffle-handed, south-pawed, spuddy-handed and plain squiffy.
2011		IOL News 5 Dec. 🌐 We revisit southpaw and orthodox greats such as Joe Louis.
2017		T. Pluck Bad Boy Boogie [ebook] ‘You’d better thrrow southpaw’.

2. in fig. use, eccentric, odd.

1921		T.A. Dorgan in Zwilling TAD Lex. (1993) 76: That bloke with the check suit is a southpaw spendthrift. He pulled out his purse here one day last year and two mice and a spiders nest fell out.
1952		E. Brown Trespass 97: Morris’ southpaw buddies. The parlor revolutionaries.
1960		G. Swarthout Where the Boys Are 130: A real southpaw compliment.