Conceptual Development: The name N. Belegund appeared in Silmarillion drafts from the 1930s (SM/297, LR/282). In the Etymologies, Tolkien defined his brother’s name as N. Baragund, with its second element as N. †cund “prince” (Ety/KUNDŪ). It is likely that in that period, Belegund was also a Noldorin name, with its initial element being N. beleg “great”.
In later writings, the language of this name is unclear. It is often assumed (as it is here) that later forms of the name are Sindarin with the same (or similar) derivations as that given in the Etymologies. However, it may be that the later form of the name was Beorian: in one place, Tolkien stated that Ed. gundu was the Beorian word for “lord” (PE17/113). See S. cund for further discussion.