事 began as a hand holding a tally or hunting tool — the doing of official business. It shares ancestry with 史 (history/scribe) and 吏 (official): all three grew from the same hand-holding-record picture. Business, recorded.
事 is the abstract 'thing' (东西 covers physical things): 没事 ('no matter' — the universal Chinese 'it's fine, don't worry'), 有事 (something's up / busy), 故事 (story — 'old matters'), 同事 (colleague). 没事没事 said twice with a wave is how China shrugs off everything from a bumped shoulder to a favor repaid. Learn 事 and you can finally ask the essential 有什么事? — 'what's the matter?'
A hand holding the official record — MATTERS to handle.
没事 'no matter' does the job of 'it's OK / never mind / don't worry / you're welcome' — four English phrases, one Chinese shrug.