Robert Downey, Jr. and his wife Susan just had the actor's second child, a son they named Exton Elias. Odd as the name may sound, it could be part of a trend -- and have geographical origins.

According to star-watchers, "X" names are hot. All three of Brad Pitt and Angelina Jolie's sons -- Maddox, Pax and Knox -- have the unusual letter in their first names. In addition, model Niki Taylor just welcomed a son named Rex, 'Mad Men' actress January Jones has a Xander, and actor/comedian Will Ferrell is father to an Axel.

But maybe little Exton's moniker is less about trends and more about maps. After all, Downey's first son, 18-year-old Indio, shares a name with the California city that hosts the annual Coachella Music Festival. Lately, though, Robert has spent a lot of time filming the 'Sherlock Holmes' film franchise across the pond in England -- a country where there are no fewer than four places named Exton.

The Downeys are remaining mum about the origin of their baby's name, but one thing is for sure: pulling a nickname out of it will be tough. As Laura Wattenberg from BabyNameWizard noted, "A nickname Ex, with its suggestion of ex-wives and ex-boyfriends, isn't likely."

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