Merc

Merc has been introduced to the American public by the network executive character on Showtime's Episodes, and is a contemporary-sounding short form of the Roman god and planet name Mercury. Mercury, from the Latin for trade or wages, was the god of tradesmen and travelers and is the fast-moving first planet in our solar system.

With the revival of many Roman names, Mercury, along with Juno and Jupiter, has a good chance of rising in the modern world. And Merc certainly is a playground-ready short form.