Marcus (Marcosian)

Okay kiddo, let me try to explain this to you in a way that makes sense. Marcus is a name, just like your name or your friend's name. Some people have the name Marcus and they come from different places in the world. Marcosian is not really a word we hear often, but it could mean someone or something related to a person named Marcus, kind of like calling someone "John's friend" because they know a person named John. I hope that helps, but let me know if you have any more questions!