Well over two thousand parents chose this ancient Roman name for their sons in the last year recorded, some perhaps honoring Marcus Garvey, leader of the Back to Africa movement. Though ancient, Marcus now sounds more current than Mark, in tune with today's trend towards us-ending Latinate names.
Marcus was commonplace in classical Rome--not surprising as it was one of only about a dozen given names in use then. Among the most prominent were the emperor and stoic philosopher Marcus Aurelius, the Marcus known to us as Mark Antony, and the politician, philosopher and orator Cicero.
Dr Marcus Welby was a staple on vintage TV, and since then we have seen the name in both the Harry Potter and Twilight franchises, as the protagonist of Nick Hornby's About a Boy, on Sons of Anarchy and Men of a Certain Age, and in Indiana Jones, The Blind Side, and Bad Santa.
Marcus Loew was the movie magnate behind MGM and Loew's theatres, and Marcus Allen was an Oakland Raiders superstar.
Marius is a related possibility.