It is not specified in the question which horse and boy you are referring to, as there are countless horses and boys that have been given names throughout history and in various cultural contexts. The naming of a horse or a boy can be influenced by a variety of factors, including cultural traditions, personal preferences of the owner or parents, significant events or qualities associated with the individual, or simply a random choice. Without specific details, it is impossible to provide a specific reason for why a particular horse and boy were given their names.
