Yeah, both the planet and the moon are both called Endor, as well as both suns. This is head canon, but I like to think explorers saw the Endor moon as the primary point of interest in the system, so they named that moon first and then named its planet and stars after it.
You might already know this, but the Emperor referring to Endor as the Sanctuary Moon is actually a byproduct of early ROTJ drafts, where Endor was originally a moon that orbited the the Imperial Capital of Had Abbadon (what eventually went on to become Coruscant). So, it was sort of a nature sanctuary that orbited the polluted, planet-wide cityscape of the Capital. So you kinda had this nature/technology contrast that George likes so much.
More head canon, but I like to think they dubbed Endor “The Sanctuary Moon” because explorers saw it as a paradise, and perhaps the Republic declared it a protected world, off-limits to development or colonization. So the name describes the the habitability or pleasantness of the world.
Maybe to contrast it, Kef Bir could be referred to something like “The Tempest Moon” to describe its violent winds and dangerous oceans. This powerful weather led to Kef Bir being a less preferable world to visit compared to its forest counterpart. Perhaps to give some credence to this name, Kef Bir’s weather could play a role in causing the Falcon to crash land on the planet. This would also be a nice way to parallel Shakespeare’s play of the same name. Since many people think of the play when they hear the word tempest, it might help add to those mystical connotations you were looking for in a potential name.
EDIT: Adding onto that, perhaps Jannah and the other stormtroopers also crash landed on Kef Bir. This could be why Jannah offers him a piece of their own ship, since it was beyond repair anyway. Maybe they were trying to flee from the First Order after their desertion, and while the violent weather of the planet made following them undesirable, it led to them being stuck there. Despite that, maybe they kind of don’t mind it, because it has kept them out of the First Order’s grip.