GI: "Government Issue"?

[Wilson Gray]

Is there any evidence of any kind, even anecdotal, to support the claim
that "GI" means or once meant "government issue"? During my time in the
military, I never once heard the term, "government issue," (and yes, I
*was* listening for it) used by anyone to designate or to refer to
anything. Terms actually used were "Army issue" or "military issue" or
"regular/regulation issue" and these were never abbreviated to "AI" or
"MI" or "RI." On the other hand, "GI" was universally used in a million
different contexts, e.g.

GI beans and GI gravy!
Gee, I wish I'd joined the Navy!
Sound off!
etc.

-Wilson Gray