Trade translates to revenues. The recorded history of early trade during the existence of early civilizations is through barter or the direct exchange of goods and services within an agreed rate (for instance, 4 pieces of apples can be exchanged to 3 pieces of oranges). The trade during early times is for the satisfaction of human needs, and not for any monetary value since the trade involves the direct exchange of products and without any trading medium.
The introduction of currency as a trading medium by the Aksumite Kingdom in northern Ethiopia started the conduct of trade that is focused on revenue generation. Early currencies used in trading such as gold, silver, and bronze coins or any other objects with value have evolved and later on became the paper money and credits that we are using today in modern trading.