Final answer:
Ge'ez was the common language among traders in the Aksumite Kingdom, necessary for commerce and communication.
Step-by-step explanation:
The common language used among the many traders of Aksum was Ge'ez, a Semitic language that survives in inscriptions. As a major trading power, Aksum was in frequent contact with other societies, fostering a rich environment for cultural and economic exchange.
The Aksumite Kingdom, known for its export of goods such as frankincense, myrrh, and gold, needed a lingua franca to communicate effectively within the diverse empire and with other regions, particularly across the Indian Ocean and Arabian Peninsula. Ge'ez played a crucial role in facilitating trade and administrative affairs, thus cementing itself as the language of commerce and governance.