UNIX was ported to the IBM Series 1 minicomputer. The Series 1 had the same
size words (two bytes) as the PDP-11, but the bytes were swapped. Hence, when
the machine started up for the first time, it printed out "NUXI" instead of
"UNIX". Ever since then, the "NUXI problem" has referred to byte ordering
problems.
[Communications of the ACM, Vol. 26, No. 12 -- December 1983]
NUXI problem /nuk'see pro'bl*m/ /n./
Refers to the problem of transferring data between machines with differing
byte-order. The string `UNIX' might look like `NUXI' on a machine with a
different `byte sex' (e.g., when transferring data from a
little-endian to a
big-endian, or vice-versa).
[ The Jargon File v 4.0.0 ]