This idiom humorously advises someone not to abandon their primary source of income or stability to pursue a risky or unlikely venture, typically one they’re not skilled at. It suggests their current job is safer than their ambitions, often used to gently mock poor performance in a hobby or side project. The phrase carries a teasing, slightly sarcastic tone, but can also be affectionate, encouraging realism without crushing dreams.

The phrase emerged in 20th-century English, likely in the 1940s, tied to the rise of entertainment culture where amateurs tried careers in music, acting, or comedy. It first appeared in British slang, with a 1948 *Punch* magazine article using ‘don’t give up your day job’ to mock an amateur performer. The phrase gained popularity in the 1960s with the growth of talent shows and open-mic nights, reflecting tensions between stable work and creative aspirations. Its use in American English, especially in showbiz contexts, was cemented by TV shows like *The Gong Show*. Its relatable humor ensured its spread to broader contexts like business or sports.