I don't have a reference handy, but I do distinctly recall reading
that Microsoft introduced the term "folder" specifically to also be
able to refer to a concept of "something which is _not_ a directory
but containing a collection of some kind of items".
Things like "My Computer", "Network Neighborhood", "Printers",
"Control Panel" and so on.
IBM also used the term "folder" no later than by OS/2 2.0 [1], but
I'm
not sure how far-ranging their usage of the term was. That would be
contemporary with early betas of Windows 95, which introduced the
term
in Microsoft's ecosystem (they used the term "folder" in
mid-1993[2],
and Wikipedia puts a first OS/2 2.0 release at October 1991).