[JdeBP]

There are no contemporary sources for that because it is, as it was called here on Hacker News some years ago, an 'ahistoric retcon'.

* https://news.ycombinator.com/item?id=31338349

The 's' is for 'static' version of the explanation of the name of sbin is not actually supported by any 20th century Unix doco. The books on AT&T Unix System 5 (before which, things were in /etc) that actually give an explanation for sbin all say system binaries, or system administration commands; and none of them says anything about linkage.

The 'static link' story came from Linux people years afterwards. Here's Ian McCloghrie correcting this misconception in a Linux discussion back in 1993:

* https://groups.google.com/g/comp.os.linux.development/c/EKzL...

I pointed out the origins of sbin some years ago.

* https://lists.debian.org/debian-user/2019/02/msg00041.html