Koolau
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
Reminds me of the days before PC's, Servers, and IP networking - Some terms, off the top of my head, that I think have died out "for the most part". Some may still fit to a degree. But there were thousands of them back in the day of mainframe data centers and networking.
Bootstrap
EOJ
MF's
FEP's
Bus and Tag
Channels
MIP's
SNA
Bisync
SWAP Space
Timeshare
Job Breakdown
Abend
EOJ
Big Iron
Punch Cards
Paper Tapes
Mag Tapes
MVS
VM
JES
DASD
LPAR's
Partitions
Green Screens
Bipolar
CMOS
Mass Store
MTO
That's enough for now. Or all I can think of in 10 mins.
Probably the oldest computer idiom is "bug" as in chasing a "bug" in the system. Probably dates to the mid 1940's. Supposedly, it dates from the days when a computer was built with vacuum tubes. Supposedly, an actual bug (as in insect) could cause issues within the system.
Even today, a "bug in the system" seems an appropriate expression, even though the original meaning is nearly lost in antiquity. YMMV