Green’s Dictionary of Slang

wang n.¹

a notable person.

1928		C. McKay Home to Harlem 232: ‘Is she the goods?’ ‘She’s a wang, boh. Queen o’ Philly.’.
1949		Monteleone Criminal Sl. (rev. edn) 249: wang A talkative person.

In phrases

on the wang (adj.)

knowing, sophisticated.

1913

Truth (Sydney) 23 Feb. 5/1: I’ve been associated / With some fellers, on the Wang / Who do know their way about, Sir.