The metaphor is of course very primitive. It is easier to illustrate than it is to explain because action came before speech. Let us make a parallel. Language is like money. In primitive communities actual goods, however bulky, are bartered for what one wants. This finally evolves into coin, the coin being not real wealth but a symbol of wealth. Still later even coin is abandoned for legal tender, and still later for cheques in certain usages.

-Zora Neale Hurston, "Characteristics of Negro Expression"