Tharael, NOT Therael, is the Problem
Worldbuilders often develop names, toponyms, and other mythonyms that resemble each other. Sometimes this is done on purpose, other times it is a coincidental outcome of generating so many new words. However, similar mythonyms can cause confusion for those trying to keep track of new elements, especially if there are a lot of them. While this may not be a problem for creators wishing to generate lengthy tomes that require great study to fully ingest, those building simpler worlds may wish to use more easily identifiable names simply for ease of use. This does not mean that designers need to give up their ancient line of kings whose name all begins with the letters Alth-, but maybe they should consider only focusing on a single lost heir to the throne at once instead of trying to introduce audiences to Altherus, his father Altheril, and his two sons Altherile and Altherule, all of whom are playing major roles in the story.