Stumbled in here after following a link from the Tech Log - lots of good gen here.
Grandad Flyer asked a question a few days ago re: "Charlie Charlie" instead of "affirm"; I've been told by various old and bolds that it dates back to the days of the early days of HF radios. I certainly use it a fair bit (RAF I'm afraid) in the Middle East and Africa - controllers 'round those parts will often say "Is that Charlie?" (instead of "Is that correct?") the reply to which is "Charlie Charlie". Hmmm.