"Quattro," a k a Windows Home Server, has been a puzzle to me, in terms of its codename. It didn't seem to fit with the other members of the Windows Server family: Longhorn Server, Cougar, Centro, etc.
The reason it doesn't mesh is that Windows Home Server, in some ways, is a product that almost didn't come to be. It took Home Server General Manager Charlie Kindel four (yep, quattro) tries to get the executive green light.
Kindel said he first began mulling the idea for a Home Server type product back in 1999, when he was a group manager on the consumer Windows home networking team. (The home networking code was codenamed "Neptune.")