Credit: Michael Buckner/Getty Images for PSIFF editors Pamela Satran and Linda Rosenkrantz -- who penned the books Baby Name Bible and Beyond Ava & Aiden -- are blogging for about why celebs choose the names they do, and what they mean.

Diablo Cody, screenwriter of Juno, obviously has a thing for names that end in the letter o: She named her new baby boy Marcello.

Dad is writer Dan Maurio; the baby's middle name is Daniel.

BLOG: Read more "What's in a Name?" columns

Marcello, the modern Italian form of the Latin Marcellus, is drawn from Mars, the name of the Roman God of War. Pronounced mar-CHELL-o, its best-known bearer is classic movie heartthrob Marcello Mastroianni, who starred in such films as La dolce Vita and had a daughter, Chiara, with Catherine Deneuve.

Cody's own name, which means "devil" in Spanish, was taken from the song "El Diablo" by Arcadia; she was born Brook Busey. The former stripper won an Oscar for her screenplay for Juno, whose title is also the name of the film's pregnant teenage heroine.

Like Marcello, Juno is also the name of an ancient Roman deity; she was the mother of Mars.  Coldplay’s Will Champion used it for his daughter.

Other fashionable o-ending names used by celebrities in recent years include Domino, daughter of India Hicks; Echo, Nick Hexum’s daughter; Enzo, used for their sons by both Annabeth Gish and Patricia Arquette; Kenzo, chosen by Kimora Lee Simmons and Djimon Hounsou; Lazaro, son of Gael Garcia Bernal; Milo, son of Liv Tyler; Madonna and Guy Ritchie's Rocco; and Taylor and Natalie Hanson's Viggo.

Middle name Daniel, after the boy's father, is a Biblical name that has been one of the most popular in the US for the past few decades. Marcello, which was given to fewer than 200 babies last year, does not register on the Top 1,000.