Expert: What Nicole Richie's Baby Name Means

Baby name expert Pamela Redmond Satran isn't surprised Nicole Richie and Joel Madden named their baby son (born early Wednesday morning) Sparrow James Midnight Madden.

"Bird names are definitely getting hotter," Satran -- who co-wrote Baby Name Bible and runs Nameberry.com -- tells Usmagazine.com. "Of all the animal names, bird names are the hottest."

A bird name also has a "spiritual symbolism: they're seen as light, one with the sky and nature and in a more uplifting, positive way than other animals, like a fox, which is more macho," Satran says. "Nicole Richie is a free spirit."

Look back at Nicole Richie's bump days

Satran also points out that Sparrow and Harlow, Richie's 20-month-old daughter, have the same ending: "ow."

But she notes that Sparrow is typically a girl's name.

See photos of more adorable star babies

"It's an interesting choice for a son because you really can't tell if it's a boy or a girl," she says. "Something we've started to see is parents being much more open to giving their sons names that have a feminine feel or are unisex."

The middle name, James, is "conventional," Satran points out, "in case they want to go by that later in life." (Harlow's middle name is the traditional Kate.) 

Midnight, like Harlow's second name Winter, denotes a time or season, which is often found in African culture, Satran says. "Some of the earliest African names in the U.S. were Afternoon, Easter, Christmas and Friday," she says. "You have to think there's some pattern [with Harlow and Midnight]."

See who else is pregnant this season

Midnight "might be the kind of name you would expect somebody trying to make it as a punk rocker to give themselves," adds Satran. Madden is the frontman for band Good Charlotte.