The name 'Belei' has ancient Slavic origins and is recorded in the southern slopes of the Ukrainian Carpathians even before the Tatar invasion. In literature, one can find the etymology of this name linked to the Bulgarian male name 'Belei', which derives from the adjective 'бѣлый', meaning 'white'.The name 'Belei' and its variations, such as 'Bieley', 'Beley', and 'Byeley', were popular in Old Polish during the 14th - 15th centuries. In Croatia, diminutives like 'Bela', 'Bele', and 'Beli' are also used, coming from similar names.In the 17th - 18th centuries, the anthroponym 'Belei' ceased to be used as a personal name and began to be used as a nickname or surname, usually to describe the color of fur or skin of animals. This name is directly associated with the adjective 'біл-' (white, light) and the suffix '-ей'. Research indicates that the suffix was not added directly to the adjective, but to shortened forms of names.Researchers emphasize that there is a large number of names derived from the root 'Bil' (or 'Бѣл'), indicating genetic connections with Proto-Slavic diminutive formations. The name of the village 'Beleiivtsi' in Prešov, which dates back to the late 16th century, confirms the data regarding the usage of this name in the region.Additionally, it can be suggested that the Carpathian form 'Belei' was influenced by Bulgarian or Polish languages. Alongside 'Belei', the surname 'Biley' has also been recorded since the 16th century, indicating local phonetic changes.