四德 originally had a male sense -
孝 piety,
悌 brotherly respect,
忠 loyalty,
信 faith - but the feminine reading from
《周礼·天官》 (
妇德/
妇言/
妇容/
妇功) became dominant when paired with
三从. The pairing
三从四德 was canonized by
《女诫》 of
班昭 (Eastern Han) and remained the conduct manual for imperial-era women until the 20th-century reforms.