Credit: Kyle Blanc/FilmMagic 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.

Happy early birthday, Liam McDermott!

It's fitting that little Liam McDermott -- son to Tori Spelling and Dean McDermott, who was born just four days before St. Patrick's Day on March 13, 2007 -- should have an Irish first name. Liam is one of the most popular Irish boys' names to hit our shores in recent decades. Along with such brethren as Conor and Aidan, it's picked up where older Irish names such as Sean and Kevin have left off.

Propelled from obscurity by Irish actor Liam Neeson, the name is actually an Irish variation of William (or Uilliam, as it's sometimes spelled in Ireland). Neeson's own first name is William, with Liam being the short form.

Rachel Hunter and Rod Stewart also chose Liam for their son, as did Calista Flockhart.

Liam first hit the Top 1000 in the U.S. in 1967, and it has been rising ever since, now hitting No. 75.  An ideal blend of the simple and the exotic, we predict it will go yet higher on the popularity list.

Liam is also in the Top 50 boys' names in Australia, New Zealand, Wales, and -- more surprisingly -- Belgium and Sweden.

In Ireland, it is No. 17, but such exotic (to American ears, anyway) Irish boys' names Cian and Oisin -- pronounced Keen and Osheen -- are ahead of it.

It's unusual, especially for a boys' name, for a short form to be taken from the end rather than the beginning of a name.  A few other examples that are stylish these days include Xander or Zander for Alexander, Drew for Andrew, Lex for Alex, and, especially popular for girls, Bella for Isabella.