The last chapter of Menger's Principles is dedicated to the problem of
money. There he uses an expression like "naturgemaesses Product der
menschlichen Wirthschaft" (natural process of human economy), but
as far as I know, he does not seem to be using a phrase "spontane
Ordnung" (spontaneous order). The same can be said of his next
methodological work.
Of course all of this does not deny that Menger was a source of Hayek's
arguments together with various Scottish Enlightenment authors,
including A. Smith.
Anyway, "spontaneous" and "order" are
bread and butter words in any western languages. I suppose that
it was very easy for Hayek to coin the new (?) terminology "spontaneous
order".
Yukihiro Ikeda