事故
shìgù · HSK 3
accident
💥🚗 事 = matter/affair + 故 = cause/reason → an incident with a cause
事 means affair or matter; 故 means cause or old reason. Together they name a matter that has a cause behind it — i.e. an accident or mishap. 故 also appears in 故事 (story) and 原故 (reason).
事 — hand 又 holding a banner/tablet on a pole
Originally a pictograph of a hand (又) grasping a pole or ceremonial banner used by an official, depicting the act of conducting court business. From this it came to mean 'affair, matter, business, service.' It shares an ancient origin with 史 (scribe) and 吏 (official).
故 — 古 (old) + 攵 (action/strike)
故 combines 古 'old' as the phonetic with 攵, a variant of 攴 meaning to strike or act. Originally it referred to a cause or reason behind an action. From this it extended to mean 'former, old, deceased' and 'therefore, hence' as a connector.