I imagine the East/West trade networks were the source of the terminology. Obviously before the "discovery" of the Americas north and south America were excluded from trade networks. But that doesn't explain why Africa would not be included.
Any and all information explaining what these terms represents and why is appreciated.
The (Global) South is used to refer to latin america, africa, and sometimes india in economic contexts. It hasn't caught on in general use because by an way you look at them besides economics, there's really nothing binding them together.
It seems this question might be more suited to a modern language sub, or perhaps a geography sub. Unfortunately, there is little historical about the question as it is.