Dot matrix printer go EEEEEEEN-futfutfut-EEEEEEEEN-futfutfut...

Well I think that is where the term comes from.

Not oddly enough. Exactly as expected. DMZ in networking forwards all ports to a specific IP address behind the firewall. That address is demilitarized. It has no firewall defending it.

I've seen it backronymed into "data management zone" in a few places, but it will always be "demilitarized zone" to me.