Now that's a good idea for a Canteen Challenge Thread for one day, "Dustoff," "JEEP," "French Leave," "Over the Hill," "Shave-Tail," "GEEDUNK," heck getting suggestions could be a Canteen Thread all its own.
Honestly though ops33 I don't know.
I'm a retired USAF air traffic controller and have talked to many, many Army helicopters using that callsign. I have always wondered where it came from. I think it may have a similar origin to the Challenge Coin. It just sorta started.
BTW, I carry my coin everyday.