There are three naming schemes present on the network at this time. This page contains some details on those naming schemes.
Initially, the only naming scheme in use was based on the computers model name. For example, a Sun SPARCstation 5 would be given the computer name "ss5" and a DEC AlphaServer 1200 was given the name "as1200". This worked well when there was only one of each type of machine. It was obvious which machine "as1200" was and for any given machine it was easy to guess the hostname.
This naming scheme did not work so well for machines without a model name (generic custom-built ones). It also became a problem when there were were multiple machines with the same model name. For example, I have two AlphaServer 800s but I cant very well have two machines named "as800".
For generic machines a new naming scheme was used based on the type of CPU. This generally worked well early on as I rarely had two machines with the same CPU. "k6" was the generic machine with the AMD K6 cpu and "p3" was the generic machine with the Penitum-III CPU. Like with the naming scheme based on the computers model, this becomes a problem when there are multiple identical machines.
Until 2009, multiple identical machines were just numbered or named based on their purpose. For example, there were three SGI Indys which were called "indy1", "indy 2", and "indy3". This isnt so easy to remember but it wasnt much of a problem because it was just three machines. Of the stacks of Compaq Prolinea 575e and Deskpro 2000 machines, only a few were ever in use at one time and normally just as print servers. So they might be given names like "ps0".
For systems with multiple network interfaces, assigning them numbers like with the SGI Indys was not possible. This is because IP Addresses are allocated to network interfaces, not machines. A machine with three network interfaces has 3 IP addresses. Each IP address needs a DNS record so a machine with three network interfaces would get three hostnames (only one would generally be used by the machine though). Because the AlphaServer 1200 has two network interfaces it is assigned two IP addresses with the DNS names "as1200" and "as1200-2".
In 2009, two AlphaStation 200s and a second AlphaServer 800 were acquired. These machines dont have any specific function and just adding a number to the model number was not possible as the first AlphaServer 800 had two NICs. Going with the old naming schemes would have resulted in:
This would have been far too confusing so a new naming scheme was chosen.
The model name based naming scheme is still used for unique machines as such names are easy to remember. From 2009 a new naming scheme is used in cases where the machine does not have a model name (because it is custom built) or when there is multiple machines with the same model name.
Such machines are now assigned names based on space objects (planets, stars, comets, whatever). Using names of planets, etc, was chosen because it provides a reasonably large number of easy to remember names. The meaning of the names is not taken into consideration when assigning names to machines. A machine will be called "jupiter" because it is the next name on the list, not because it is large or because it is like the roman god of the sky and thunder.