To unload a
DECtape (so it goes flap,
flap, flap). Old-time hackers at
MIT tell of the days
when the disk was device 0 and microtapes were 1, 2,
etc. and attempting to flap device 0 would instead start a
motor banging inside a cabinet near the disk.
The term is used, by extension, for unloading any magnetic
tape. See also
macrotape. Modern cartridge tapes no
longer actually flap, but the usage has remained.
The term could well be re-applied to
DEC's TK50 cartridge
tape drive, a spectacularly misengineered contraption which
makes a loud flapping sound, almost like an old reel-type
lawnmower, in one of its many tape-eating failure modes.