You've heard of the 'gig economy', but what is a gig? Well, it's a spinning top, a two-wheeled horse carriage and a type of fishing hook. Mainly, though, it is a casual job for a musician, particularly a 'one-night stand'.
The word was first used in the 1920s, by jazz and dance-band players, but nobody knows its derivation: perhaps it comes from 'engagement'. In America, 'gig' has long been applied to any short-term job; we've only picked up that usage recently. Life as a gigging musician can be rewarding, but more often it is perilous. Now we can all try it.