If you spec your Death Knight as Unholy, 30 points into the talent tree you get the Master of Ghouls ability which lets you control your ghoul like a pet. On the PvE beta realms, your ghoul doesn't have a name yet; it comes up "RandomPetName," as pictured to the right. However, on the new Murmur PvP realm (US only), level 80 Death Knight premade characters are getting names for their pet-ghouls. An enterprising poster on the beta forums is compiling a list of possible names using set prefixes and suffixes they've seen. Here's the list so far.
Basically, the ghoul names come from picking a prefix from column A and combining it with a suffix from column B. I hope my ghoul's name comes out to be GraveFeeder or CorpseCruncher. However, as you can imagine, some of these name combinations just will not fly as they may sound too R-rated. (In particular, Blizzard might want to consider killing the "Muncher" suffix altogether.) Similar to a Warlock's minion name, it appears that the ghoul's name stays constant, even after dismissing and resummoning. Blue forum poster Ghostcrawler says that generating a random name for every summon requires a code change that won't happen before Wrath hits. However, Ghostcrawler does say that the randomizing code will likely be included in a post-Wrath release.