People sometimes will name their voicebank 'unconventional' names like dark, bright, etc. Think of how Miku has all sorts of Appends, a few of which are 'Vivid', 'Solid', 'Dark', etc. UTAU creators usually will name their vb whatever they feel like fits as a good vocal descriptor, but there are some voicebanks with strange names like 'bubblegum' or 'cotton candy', even though those don't directly correlate to voicetypes.
My own UTAU for example is a personified typewriter, so his voicebanks usually get some sort of typewriter part added to the end of the name to differentiate between them! His latest released VCV is called 'platen', and his unreleased (but hopefully soon to be) VCV remake is named 'inkribbon'.
A friend of mine (
@Sors) has named one of his voicebanks
Snowflake!
There are really no rules or regulations! You're free to do what you want, but if you're naming the voicebanks different things because you're aiming for different tones for each bank, a description of what the bank is is really useful if you decide to name it something that isn't directly related.