The answer
It was so called because if a person obeys God, it becomes to him the Tree of the Knowledge of Good; and if he disobeys God, it becomes to him the Tree of the Knowledge of Evil.
Fr. Tadros Yacoub Malaty
Fr. Tadros Yacoub Malaty · Catechism · 321
Faith Q&A › Catechism › 9. The Fall of Humanity
Why was the tree called the Tree of the Knowledge of Good and Evil?
Fr. Tadros Yacoub Malaty, Catechism of the Coptic Orthodox Church, Volume 1, Books 1–3. First English Edition, 2023. Published by St. George Coptic Orthodox Church, Sporting, Alexandria, and Queen St. Mary & Prince Tadros Coptic Orthodox Church, South Brunswick, NJ. Copyright © 2023. Translation and Editing: Youth of the Coptic Orthodox Church in the USA, Canada, Europe, Australia, Arabian Gulf, and Egypt.