Moonlighting

Etymology

From the image of working “by the light of the moon,” at night after the day’s main job. In nineteenth-century Ireland “moonlighter” carried a different, darker sense — nighttime agrarian raiders — but the modern second-job meaning took hold in the mid-twentieth century.

noun · /MOON-ly-ting/
Holding a second job in addition to one’s main employment, typically outside regular hours.
What it names
The specific arrangement of a hidden or after-hours second income, distinct from openly juggling multiple gigs.
Example
She was a teacher by day, moonlighting as a bartender to cover the rent.
Related idea
Overlaps with the side hustle, but tone differs: a side hustle is proudly public and often entrepreneurial, while moonlighting connotes quietness and sometimes a conflict with the primary employer, shading toward overemployment when jobs are concealed from each other.