Green’s Dictionary of Slang

(US black/campus) excellent, wonderful.

1956		O. Duke Sideman 98: Coke’s a wailing cat.
1959		Mad mag. Sept. 41: It’s for us, the on-cats, who ought to pick up on those still-wailing blues.
1964		R.S. Gold Jazz Lex. xxii: Currently, in response to an inspired musical performance, a jazz devotee draws from a large storehouse of terms: crazy, nutty, insane, swinging, groovy, cooking, wailing, burning, smoking, boss, something else, out of sight, etc.
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 44: (a) wailing cat – This stud is turned on all the time and there’s no stoppin’ cause he’a finger-poppin’.