How did the errno variable get its name?
Maybe somebody from Bell Labs who was there a
few decades ago when C and the Unix system calls
were invented will answer this. Otherwise, some
mind reading appears to be called for.
There have been systems where variable names were
constrained to fit in as few as 6 characters. And many
people are adverse to abbreviations other than well
known ones. (If they were adverse to abbreviations
on 6-character systems, they had a very hard time.)
So, to me, 'errno' is the least surprising name, given
its function and the fact that mixed case was not in
favor among the crowd that devised those names,
at least not at that time. (Remember, this was when
the "glass teletype" was a newfangled thing and many
output devices did not display lower case at all.)
I always figured it's short for "error number", but then it would have
been better to call it errnum... no?
'No' is a commonly used abbreviation for 'number',
so better is certainly not clear.
(Come to think of it, this is probably a C question, so my apologies if
it is indeed offtopic)
I believe errno is mentioned in the C++ standard
since it is part of standard C (or ex-standard C)
by reference and errno is well covered there.