[ 3 syll. cas-siu(s) , ca-ssi-us ] The baby boy name Cassius is pronounced as K AE S-iy-ahS or K AE-SH-ahS in English â . Cassius is used predominantly in the English language and it is derived from Latin origins.It is from the element 'cassus' meaning empty, vain.The first name is derived from Cassius (Latin), the surname of one of the oldest families of Rome.assius is somewhat popular as a baby name for boys. The name's popularity has been increasing since the 2010s. At the modest height of its usage in 2011, 0.012% of baby boys were given the name Cassius. Its ranking then was #876.