Origin: Germanic Old English suffix
Moonlight has 4 different meanings across 2 categories:
The light reflected from the Moon.
"The silver glow on the lake was caused by moonlight reflecting off the calm water."
In plain English: Moonlight is the light that comes from the moon at night.
"The children played in the garden under the bright moonlight."
Usage: The noun refers to natural illumination, whereas the verb describes working at a second job outside one's primary career. Do not use "moonlight" as a verb when simply describing something that is lit by moonlight.
To work on the side (at a secondary job), often in the evening or during the night.
"After his day shift at the warehouse, he took up moonlighting as a freelance photographer to earn extra cash."
In plain English: To moonlight means to do an extra job at night while having another main job during the day.
"The shy teenager moonlit across the crowded room, trying to avoid everyone's eyes."
Moonlight comes from Middle English, where it originally referred both to the illumination provided by the moon and to a heraldic pattern featuring moons on a banner. While its components are simply "moon" and "light," the word entered modern usage specifically to describe natural lunar illumination rather than any decorative design.