[WaitWaitWha]

Old man talking about both ways up hill:

Historically, we did not have wifi and other radio based new fangled data communications. Data connectivity required wires, physical connections. If there was a gap between the two devices that had no wire, just air, that was air gapped. No comms could happen between the two. It is physically isolated. it used to be called "physically isolated" when we used it in the 80's (?). Some say, we stole it from plumbers but that is hogwash (pun intended, you know the backflow prevention thing). I vaguely recall start seeing it late 1990's to 2K in the public?

Mission Impossible 1996 the computer in the room where tom cruise is lowered into the room. That was an example of 90's air-gapped system.

The name stuck because it sounds cool. In my opinion, there is no such thing as true "air-gapped network" any more. There are too many ways to snoop on systems that are isolated, without "physical" and radio connections in the traditional sense (e.g., listen to the "electricity", sounds, power fluctuation, ground vibration, squirrel squeeks).