事故
じこ · jiko · JLPT N4 · noun
accident
🚗💥 事故 = incident (事) + cause/reason (故): an incident with a cause
事 means matter or incident, as in 仕事 (work) and 火事 (fire). 故 means cause or circumstance, as in 故障 (breakdown). Sound hook: jiko is close to GEICO, the car insurer you call after an accident.
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.