During the night or from one day to the next. As an adjective, describes something that happens suddenly or very quickly.
Compound of 'over' and 'night', first appearing in Middle English. The sense of 'sudden' or 'very quick' developed from the idea that significant change happened in just one night, which seemed impossibly fast.
The phrase 'overnight success' is deliciously ironic since most 'overnight' successes actually took years of preparation! The metaphor captures our amazement when someone's long invisible work suddenly becomes visible to the world.
Complete word intelligence in one call. Free tier — 50 lookups/day.