When designing a world it is convenient to decide how places will be named: Elements like the continents and the oceans.
However, it is likely that the different cultures of the world will not agree on a common name for these places. Some might not even know there is an ocean or maybe they just don't care and will simply use the name already given to that place by others.
An example of modern naming dispute.
On Earth, a lot of places have the names they have now because the Europeans established the conventions. On the other hand, I know that the norms do not apply everywhere. For example, China is Zhōngguó (中国) in mandarin Chinese. It's not a translation of China, the meaning is very different. China comes from the Qin dynasty that established contact with the Europeans a long time ago. People in China will probably not use China to talk about their country unless they speak with foreigners.
How do we solve this issue in world-building? In real life, we would have an atlas in our own language and places would be named accordingly. Original names of other languages are harder to understand for those that do not speak the language.
- Sometimes, the names are written using the same phonetic but adapted for the language : Beijing becomes Peking
- Sometimes the name can simply be translated: United States, États-Unis (French)
- Other times, it's completely different like with China
When making a map and designing a world, we can't have multiple names for each place, it's far too confusing. Maybe they could have multiple names but we got to have a common name at least for designing purposes.
- We could have a culture dominating the world that imposed the names.
- We could only use the local names for each place but what do we do when we have multiple names as for the oceans?
- We could build the world using only one culture point of view? (even if that culture is not dominating the world)