David's surname is taken from the name of the Roman military camp established in ancient Barcelona, Spain.
As one Zudite has noted in the comments, David is the dragon alluded to in the original Dual synopsis. That synopsis was written after a Dual outline, but before the scripting process. Some changes have been made between the synopsis and the finished script. The spelling of Carina’s name changed as well as her character. She didn’t end up being quite so unstable in the finished draft. Also, Liz turned out being something slightly different from a werewolf.
If we return for a third season, we may get to see a little more of the synopsis play out.