And also not entirely correct. The 16-bit 1.x API was definitely x86-specific. But the 32-bit 2.x API was not, as evidenced by OS/2 for PowerPC actually existing at one point.
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:
If you had been born in the 1960s, you might well have learned by dint of being alive at the time that the world underneath /usr was pretty complicated in the 1970s, 1980s, and 1990s; that /etc was where some of the things that were used to boot the system once went; and that the tale of sbin is complex and slightly sad.
The tale that things were simple until they went to pot in 2000 is wholly ahistoric.
1. The history of /usr subdirectories is a lot more complex than that. There was a /usr/lbin once, for example.
1. /usr/local is not where third party softwares from packages/ports go on "the BSDs". On NetBSD, they go in /usr/pkg instead, again exemplifying that this is quite complex through history and across operating systems.
I really should write that "Yes, Virginia; executables once went in /etc." Frequently Given Answer.
Because it was /etc (and of course the root directory) where the files for system boot and system administration went in some of the Unices of yesteryear. In AT&T Unix System 5 Release 3, for example, /etc was the location of /etc/init, /etc/telinit, and /etc/login .
sbin is actually quite complex, historically, because there were a whole lot of other directories as well.
