There is a classic scene on an episode of I Love Lucy regarding this word. The Ricardos and the Mertzes are being tutored in Proper English. One of them answers a question with "OK," and the tutor tells them:
"Did you say 'OK'? We must rid our vocabulary of slang. Now, besides 'OK,' there are two other words you must never use. One of them is 'swell,' and the other one is 'lousy.'"
Fred replies: "Give us the lousy one first."
The tutor gets flustered because his students don't understand his meaning. He asks for a glass of water, and Lucy replies, "OK" as she gets up. Then she catches her error:
"Oops. I would say 'OK' - that's a swell way to get off to a lousy start."