There appears to have been a few other parents such as yourself who've done the same ;)
This woman also "made up" Gabrien for her son, and poster Andy provided some possible inspirations:
http://www.behindthename.com/bb/fact/152416 including a town and a man from the 1700s!
There are a few people named Gabrien listed here as well:
http://www.linkedin.com/pub/dir/?first=gabrien&last=&search=Search And googling the name returns many results as well.
It was apparently submitted as name here a few years go:
http://www.behindthename.com/submit/name/gabrien
My PNL = http://www.behindthename.com/pnl/37275
Top: Henry & Lara (main) / Caspian & Briar (GP) / James & Georgiana (top25)
Bottom: Randall & Memphis (main) / Dinadan & Melpomene (GP) / Owain & Itonia (top25)