Cutty Wren
Now, the cutty wren is perhaps the most pathetic figure in British folklore, and if you wanted to think of a less ferocious, heroic or powerful image to name a warship after you probably couldn't do it. In an ancient Celtic tradition common through the British Isles and a few spots in Europe, a wren is killed and paraded through the streets, typically on Boxing Day/St. Stephen's Day. The ritual is the subject of several versions of folk songs. It is reminiscent of the king-changing customs described in Hogfather and may recall Druidic human sacrifice.
In Nation, the Cutty Wren is not actually a warship, it's a passenger and cargo-carrying clipper belonging to The Company (which coincidentally belongs in large part to Daphne's Grandmother). It is, however, the fastest and most reliable ship available when the Russian influenza has destroyed much of Europe's human infrastructure and the kingdom's history depends on a fast and reliable ship. The Gentlemen of Last Resort are well acquainted with Sir Geoffrey, the Company's Chairman, and Cutty Wren's Captain, Lionel Samson is soon persuaded to become His Majesty's courier.
She is more capable than many Ships Taken Up From Trade (see Navy) and succeeds in fetching the heir to the throne, even with the extra weight and distraction of Daphne's Grandmother aboard.
Superstitious sailors may be able to use some reverse psychology when crewing a vessel named for a symbolic tragic victim. The Cutty Sark was, after all, named after an item of ladies' underwear.