John O'Hara thought this synonym for well-drilled was a corruption from the Italian, but the OED and the Random House American Slang assert that its origins are uncertain. Wentworth and Flexner posit the Louisiana Creole French coupe-setique.
ERUDITION AND slangy wit are the stock-in-trade of the music critic Will Friedwald. He supplies notes for a new CD collection of vintage sides by June Christy and Peggy Lee, "almost all with highly copacetic small group jazz backing". Not a gap in a classical education, for, variously spelt, it surfaced around 1919 in Harlem, became a dance group's name, and, 50 years on, went across the universe, when Mission Control in Houston informed the astronauts, "Everything is in copacetic order."