I've challenged people on both WordPress and Shapeways to answer this, but none have bothered. See, in the story I'm working on (see my WordPress blog for more), there are four mysterious airships known as the black triremes: the Zaphnora, Grugnula, Khrodanau, and Pherazmil (somebody please tell me how me to italicise ship names here). Below is a picture of the four:
The ships are in the order that I named them, with the Zaphnora in the foreground. Here are some more views:
If you wish to learn more, you can visit the product pages in my Shapeways shop, where I have some information in the product descriptions:
https://www.shapeways.com/shops/steampunkkaja?section=Steampunk+Airships&s=0
There is also some more information in some of my old posts about the airships of the Nine Empires:
https://kjworldsong.wordpress.com/2017/06/02/airships-of-the-nine-empires-part-1/
https://kjworldsong.wordpress.com/2017/06/07/airships-of-the-nine-empires-part-2/
https://kjworldsong.wordpress.com/2017/11/02/the-aeronautical-development/
In any case, here's the challenge: tell me what those names have in common (hint in the tags)! Seriously, I'd like to interact with the few followers I have a bit more!