but it could have been "Shared" or "Resources".
You see what I mean?
A bit of history:
Initial idea was to put everything that is essential for the system to boot to the root filesystem (/bin, /sbin etc).
While user homes, docs and useful tools (like "vi") were installed in "/usr".
Apps in the root were compiled statically not to depend on anything.
Some OSes (especially BSDs) used different filesystem options for the root (noatime, no soft updates (it was before journaling filesystems were created))
Some Windows users install the system to "C:" and all applications, docs and files to the "D:".
"D:" was like "/usr" here.
But things changed, at least in the Linux world (AFAIK OpenBSD still uses "classical" hierarchy):
Debian now merges several folders inside of "usr":