New parents Ashlee Simpson and Pete Wentz gave their baby son the middle name Mowgli, because they fell in love over the Jungle Book.

Bronx Mowgli was welcomed into the world on Thursday at Los Angeles' Cedars-Sinai Medical Center.

The choice of names has left fans and celebrity pals scratching their heads.

Wentz reveals Mowgli was inspired by the lead character in Rudyard Kipling's classic story - but he's refusing to reveal why they chose Bronx, also the name of one of New York's five boroughs.

Speaking on Ryan Seacrest's radio show on Tuesday, Wentz says, "The Jungle Book was something that me and Ashlee bonded over. It's a cool name.

"We came up with the idea Bronx. We've been throwing (ideas) back and forth for a while. It's kind of cool to just leave the narrative what it is. People are stoked or p**sed or whatever... I don't think anyone really has the real story."