oral tradition
noun [ U ] uk/ˌɔː.rəl trəˈdɪʃ.ən/ us/ˌɔːr.əl trəˈdɪʃ.ən/
口头传统，口头文化（某一群体对其信仰、习俗、历史的传承，由父母口头传授给孩子，一辈一辈传授下去）
a system for preserving a group's beliefs, customs, and history, in which parents tell their children about them, and the children tell their children, and so on