Planetary nomenclature, like terrestrial nomenclature, is a process used to identify a celestial object, like a planet or satellite, so that the object can be easily located, described, and discussed. The procedure has various steps, as instructed by the International Astronomical Union. Here is a step for naming moons, as listed on their website:
“When the first images of the surface of a planet or satellite are obtained, themes for naming features are chosen and names of a few important features are proposed, usually by members of the appropriate IAU task group.
As higher resolution images and maps become available, names for additional features may be requested by investigators mapping or describing specific surfaces or geological formations.
At this point, anyone may suggest that a specific name be considered by a Task Group, but there is no guarantee that the name will be accepted.”
That seems fair. And yet, somehow, some time ago, a young astrophysist discovered that moons can have their own moons.
“An amazing find, Gary. We were unaware of such objects. Considering you discovered the first object orbiting a moon, what would you like to call it?”
Gary: “LET’S CALL IT A MOONMOON!!!”
You can read the article here.
Source: New Scientist