I just learned air-gapped includes private networks. I was under the impression this strictly meant isolated non-networked computers. Was this always the case or has the term diluted over time?
Strictly speaking, air-gapped originally meant physically isolated, no network connections at all. But in practice, the definition has broadened a bit, especially in enterprise and defense settings.
Today, it may include closed private networks with no internet access, still isolated, but with internal connectivity for practical reasons (like backups, logging, or internal auth).
I think it just depends on the context you're talking about. Air gapped just means there's no connection between two things so it could be talking about networks or individual computers.
I work on an air-gapped network. The most important thing that the words "air gap" communicate is that there is no connection, nothing at all, to anything outside the network. The only way to move anything on or off are using disc drives (no USB for security reasons). The word "private network" does not really communicate that there is a physical gap of no wires at all from the computers on the network and everything else on the internet.
Today, it may include closed private networks with no internet access, still isolated, but with internal connectivity for practical reasons (like backups, logging, or internal auth).