Since it seems from some of these responses that no one read the link I posted, here it is:

COPACETIC
Fine, excellent, going just right.

It's possible that this word has created more column inches of speculation in the USA than any other apart from OK. It's rare to the point of invisibility outside North America. People mostly become aware of it in the sixties as a result of the US space program—it's very much a Right Stuff kind of word. But even in the USA it doesn't have the circulation it did thirty years ago. Dictionaries are cautious about attributing a source for it, reasonably so, as there are at least five competing explanations, with no conclusive evidence for any of them.
One suggestion that's commonly put forward is that it was originally a word of the African-American community in the USA. The name of Bill "Bojangles" Robinson, a famous black tap-dancer, singer and actor of the period round the turn of the twentieth century is commonly linked to this belief about its origin. Indeed, he claimed to have invented it as a shoeshine boy in Richmond. But other blacks, especially Southerners, said later that they had heard it earlier than Mr Robinson's day. But he certainly did a lot to popularise the word.
A second explanation that's given credence is that it derives from one of two Hebrew expressiona, hakol b'seder, "all is in order", or kol b'tzedek, "all with justice", which it is suggested were introduced into the USA by Yiddish-speaking Jewish immigrants. Other accounts say it derives from a Chinook word copasenee, "everything is satisfactory", once used on the waterways of Washington State, or from the French coupersetique, from couper, "to strike", or, in a hugely strained derivation, from the cop is on the settee, supposedly a hoodlum term used to describe a policeman who was not actively watching out for crime, and so one who was OK.

World Wide Words is copyright © Michael Quinion, 1996–2003.

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