Naming places has a few unique considerations.
In our modern world, at least in the United States, few of us have any idea why any location bears its name. This may be true in our invented setting as well, and likely depends on how old places are. Since many places are named for someone, the person for whom they are named also has an impact if that association is remembered. Being named for someone that a culture has forgotten relegates the connection between person and place to the unknown. This is also affected by how long ago that person lived.
For example, we assume anywhere named Washington is named after the first president, but Dallas is just Dallas. In reality, the latter is named after George M. Dallas, but few know that, care, or have any idea why they should. In a world where travel is easy, such ignorance is more likely due to the sheer number of distant places (over a hundred miles) we can visit. But in a fantasy-like setting with restricted travel and far less information about the wider world, it’s more likely that people know why each location within a certain distance bears its name. This is partly due to a lack of information overload that comes with technology. Consider this before spending too much time inventing justifications for names; your characters may be unlikely to know or discover this and we therefore have little reason to worry about it ourselves.
In a single work, we should avoid explaining the reason every place bears its name. It can start to sound like we’re educating the audience or doing exposition housekeeping. Strategically pick the one or two places that are worth this, and briefly sneak in any such exposition. We decide based on whether the place’s name and its origin can characterize the setting or not.
We can have our characters see a statue, painting, or carving, at city gates, on flags, on awnings, or on prominent buildings, possibly with a plaque that commemorates the namesake. Something that depicts the person is a little better because their appearance can give an idea who they were without explanation.
For example, “As he entered the gates of Kierdon, Antar smirked at the statue of Kier looming overhead, sword aloft, plate armor emblazoned with the knighthood’s symbol, cloak swirling around him, for if Kier had still lived, he would’ve been mortified at the squalor and seediness that scurried around the town.” We would then go on to paint more details about what Antar experiences as he goes about his business, hopefully making this relevant, too, such as someone stealing from him along the way. We could alternatively have him being chased through town by ruffians before finding himself cornered beneath that statue, which adds commentary to what’s occurring.
We can invent place names using several rationales and techniques discussed next.