Viruses were a favourite for a while (Hanta, Ebola, ...)

We had a 'bad idea' theme once which included:-

    port23
    dotat

But my favourite for one of our build machines and appeared in -version output of our product was sigsegv.

I've settled on the elements with atomic number as last octet and the handy shorthands, but that's for home dev network.

For company stuff they get named by function/env/counter.