Sorry chaps but you are all wrong. The real origins of this phrase comes from the Big Airways long haul checklist that is done in cockpit, prior to push back.

The top men at Big Air require Captain Nigel and F/O Tarquin to go over all things needed for their fifteen night stop-over in Miami. It runs as follows:

1/. Hosties.
2/ Fat wallet.
3/ Charlie.
4/ Box to keep wedding ring in.

So when the check for Charlie comes up, the reply is "Charlie", hence Charlie, Charlie.

P7;)

PS Yes I'm back after short delay due event cancellation.