Hmmm,
Chasing down people relentlessly. Constatly hounding them to ground. Slowly, slowly pursuing them until they drop from exhaustion, unable to even crawl anymore.
What name's could possibly inspire so much fear?
Well, I'm guessing Barney & Richard Simmons, despite their fear inducing prowess are probablly right out.
Option 1: Steal a name. If the PC's get it, all the better. As mentioned, the fey of celtic/irish lore could put real fear in your players (if they get it). Of go with more well known names from works like Moorcock's Elric & Corum (Arioch springs to mind), or pull out your Encyclopedia Cthuliania & pick out a name that fits. Or try google.
Option 2: Bash keys until you get something you like (such as Arhgvnhynt).
Option 3: Irony, as mentioned. Something like Grace of Fox or Forest's Friend.
Option 4: Name has been lost. Gone so long no one can remember it's name (really nice if you use anything involving True Names and the power that yields.
Option 5: Beer/Wine/Tobacco. Go to the Liquor section of a local supermarket (of a high end tobacco shop). Read those labels. You want cool villain names: Wine & Tobacco has served me faithfully. I mean, over the years I must have ripped off an entire wine cellar. While a wine expert might find it hilarious that the BBEG is named after a nice chardonnay from Tuscany, what your players don't know won't hurt them.
Try the wine thing (trust me).