That isn't where that system originated. It goes back to the Persians, mycaneans, Egyptians, and nearly the whole civilized history of the near east. Probably the most recorded widespread Era of this was the middle to late bronze age. It was an ever changing patch work of large empires with their "kings of the world" imposing their authority over smaller kings of territories. The tradition goes back as far as the sumerians. Another example is when the hittite emperor writes to the mycanean king and calls him a "great king" and differentiates between that kings Control over his petty kings. The same can be seen between Egypt and the hittites in the treaty of kadesh.