The Nameless is Brazel and Grond’s ship. Brazel is the pilot (the cockpit is sized for gnomes) and Grond copilots and operates the weapons systems through a remote chair installed in his quarters. The Nameless is only lightly armed, but is a fast and capable boat and has decent shields for something its size.
The most significant detail about the Nameless is its AI, generally called “Namey” by Brazel and Grond. Namey is, to put it bluntly, a rude, sarcastic pain in the ass, and both Grond and Brazel have frequently threatened to reprogram him into something less obnoxious. Neither have attempted to follow through on the threat, however, and the ship is intelligent enough to be aware of the implications of this fact.
If there is a story behind the Nameless acquiring its unusual name, it has not been revealed yet. It has nothing to do with the author having been tired of naming things at the time, and was absolutely not a placeholder name that somehow stuck and now has to be explained in-universe. Not at all.