Green’s Dictionary of Slang

(US black) important, special, superior; usu. in derog. contexts.

[1776		O. Goldsmith Haunch of Venison 5: To be shown to my Friends as a piece of Virtù; / As in some Irish houses, where things are so-so. / One Gammon of Bacon hangs up for a show].
1912		C. McKay ‘Flat-Foot Drill’ Constab Ballads 13: Fabour say you pick up nong, / Sence you [...] sleep ’pon so-so mat, / But a mean fe pull you tongue.
1929		M. Beckwith Jamaica Proverbs (1970) 76: John-crow say him a dandy man, same time him hab so-so fedder.
1966		(con. 1930s) L. Bennett ‘De Royal Commotion’ in Jamaica Labrish 118: Den him put awn one ole ragged up shirt, / An one hat dat was so-so frame.
1980		E. Folb Runnin’ Down Some Lines 50: I jus’ hate a nigger cop that thank he so-so because he got a badge and a gun on.