The first thing you should know if you are considering Cassius for your baby's name is that in most countries all over the world the name Cassius is a boy name.The name Cassius is of Latin origin, and is used mostly in English speaking countries but also in a few other countries and languages of the world.assius Name Meaning. The meaning of Cassius is âVain, emptyâ. Keep in mind that many names may have different meanings in other countries and languages, so be careful that the name that you choose doesnât mean something bad or unpleasant.