I just finished Brian Kernighan's book (excellent!) and he addresses
this in section 7.6. (Yes, he wrote the book in troff.)

He prefers "Unix" and wrote it that way except for this section. He says
"Bell Labs' legal guardians decided that the name Unix was a valuable
trademark that had to be protected..." Legal mostly required it to be
used as an adjective "The UNIX TM operating system", and how the ms
macros produced a small caps "UNIX" (and a footnote on the first
reference). He's clear that the 1127 folks hated the requirements from
legal.

It is true that the file which contains the kernel was /unix, or /vmunix
for Berkeley Unix, but that's the name of the file, not the proper name
of the operating system for English prose.  By convention, virtually all
Unix files were in lower case.

     Mary Ann

On 11/9/19 12:36 PM, Derrik Walker v2.0 wrote:
> On 11/9/19 12:20 PM, Nemo Nusquam wrote:
>> I was reading the comments on Hackaday on UNIX at 50
>> (https://hackaday.com/2019/11/05/will-the-real-unix-please-stand-up/).
>> As expected, a lot of manure but some interesting comments from
>> seemingly knowledgeable people.
>>
>> One comment
>> (https://hackaday.com/2019/11/05/will-the-real-unix-please-stand-up/#comment-6192977),
>> from a DDS, stated that (s)he worked at The Bell and they wrote it
>> "unix" (lower-case) to distinguish it from MULTICS.  Anyone care to
>> comment on this?
>>
>> N.
>
> It was always my understanding, based totally on hearsay from
> engineers from both Sun and SGI back in my early days with it, UNIX is
> the OS, while unix, or vmunix is the kernel. Unix was deprecated by
> the time it became a real commercial product.
>
> So, right or wrong, I've always used UNIX for the OS, and unix, or
> vmunix as appropriate, to refer to the kernel.
>
> - Derrik
>