Nubia, also known as Kush, was located south of ancient Egypt, with its northern boundary at the First Cataract of the Nile River. The Egyptians traded gold, incense, ebony, copper, ivory and animals through Nubia from tropical Africa, and it is believed the Egyptian word for gold, "nub", gave Nubia its name. Slaves and prisoners worked the gold mines of Nubia, which was an important source of gold for Egypt.