From the second edition (1989):
(kəʊpəˈsɛtɪk, -ˈsiːtɪk) Also copesetic, etc., k-. [Origin unknown.]
Fine, excellent, going just right.
1919 I. Bacheller Man for Ages iv. 69 ‘As to looks I'd call him, as ye might say, real copasetic.’ Mrs. Lukins expressed this opinion solemnly.‥ Its last word stood for nothing more than an indefinite depth of meaning. 1926 C. Van Vechten Nigger Heaven 286 Kopasetee, an approbatory epithet somewhat stronger than all right. 1933 N. Ersine Underworld & Prison Slang 29 Copissettic, all right, okay. 1934 Webster, Copacetic, capital; snappy; prime. 1934 J. O'Hara Appt. Samarra (1935) i. 24 You had to be a good judge of what a man was like, and the English was copacetic. 1937 Amer. Speech XII. 243/1 ‘Everything is copesetic’‥is synonymous with ‘O.K.’, and I believe it is used by negroes in the South. 1947 Down Beat 18 June 4 (heading) Torme not all copa-setic. 1969 Ibid. 20 Mar. 18/1 We hear two city cops chatting. ‘Well, everything seems copasetic,’ says one. ‘Yeah, we might as well move on,’ the other agrees.