Nicknames:
Dem, Demi, Demitri.
Famous people named Demetrius:
Rappers Demitrius Pugh and Demitrius Stewart (a.k.a. Shawty Redd); actors Demitrius Joyette and Demitrius Grosse; boxer Demitrius Andrade.
Fun fact:
Demetrius was apparently one of Shakespeare's fave names, since he used it for characters in three of his plays.
More Inspiration:
150+ Boys Middle Names That Hit The Sweet Spot Of Unique And Traditional, Dashing D Names For Baby Boys,