Arlo is a Spanish nature name (it means "barberry tree") and has generally been far more popular for boys. It's been on a huge uptick in the past few years, and currently sits just outside the top 500 baby names for boys.
Singer-songwriter Arlo Guthrie is the biggest claim to fame for this name, which was first used in Edmund Spenser's classic The Faerie Queene. But on the girls' side of things, Jackass star Johnny Knoxville also picked it for his daughter, and it fits in well with all those Marlow(e)s and Harlow(e)s on the celebrity baby front.
Day is obviously a word name, and a fresh and optimistic choice at that. I think it makes a really intriguing (but not too out there) middle name pick.
All in all, I think it's a really stylish baby name pick—just out there enough to make it unique, with a nice bit of history behind it. And I think it'd be equally cool for a boy, too.
Tell us: What do you think of Meester and Brody's pick? Would you give Arlo to a boy or girl?