"Not a typewriter" is an
error message found in
Linux libc5 that was often seen in
good old days of 0.x
GNOME.
Funny if you know what it means,
obscure if you don't.
Sadly, the error message was corrected in glibc2 (aka libc6) to less cryptic form (still probably doesn't make too much sense for newbies, but hopefully tells more of the cause of the message): "Inappropriate ioctl for device".
(The corresponding errno code is ENOTTY. Well, the original Teletypes looked a bit like typewriters, but that's not what ttys are thought to be these days...)
Interestingly, the message still lives in glibc headers (as of 2.3.1), can be still found in the comments in /usr/include/asm/errno.h (that's included via many ways with #include <errno.h>...)
See also: "lp1 on fire" (never seen that personally, though - and apparently that went out of the window in Linux 2.4.20, too).