–Unsure on Surname
This is an unusual surname solution, but not an unprecedented one. Rather than expecting "trouble," expect some questions and confusion. The good news is, you have a ready answer to those queries: You want to keep a cherished family surname alive.
Yes, people may mistakenly assume that you are a blended family with kids from previous relationships. Close friends and even acquaintances can easily be set straight. And for one-time encounters, who cares?
Dad, I think we can put your fears to rest—especially if Eliot would be your son's middle name, not his surname. It’s a huge stretch to think that 8 or 10 years for now, some classmate will learn William’s middle name, consider that Billy is a traditional nickname for William, and then make a connection to an old movie (it came out in 2000) or Broadway musical (which debuted in 2005). After all, the Billy Elliot character is far, far removed from the Marvel or Star Wars universes.
Forgive me, Nana, but I am going to read between the lines of your question, because I'm seeing a powerful unspoken message here. You're asking me—the name expert—to validate your suspicion that this name isn't "real." Once you have that, you can object to it more politely (you didn’t say it; the Name Lady did!).
–Harriet's Mom... and Kit's?
I've written many times before about the particular complications that come with naming a second (or later) child. The universe of available names narrows once a limiting factor is introduced. The meaning, nation of origin, cultural associations, and sounds and letters of an older sibling's name all dictate, to an extent, what the younger will be called.
As you've probably guessed, there's likely more going on here than just a simple preference for one name over another. The underlying issue is whether your mom is rejecting just the name Alois, or your entire new gender identity.
I can certainly see the charm in this choice. Gotham is a clever way to pay tribute to the superhero without actually naming your child Batman (not recommended!), or Bruce, or Wayne. Batman's civilian names read much more '60s and '70s than superhero. As a place name, Gotham sounds far more fresh than names associated with your baby's grandparents' generation.
–Worried About Stealing
Wading into the waters of name "stealing" is always tricky. While it's true that no one owns a name, and theoretically you should be able to use any name you like, you specifically asked about "etiquette." Etiquette means caring about other people and trying to be considerate of them. It means not making the (arbitrary) decision that your claim to a name is more legitimate than someone else's, and that therefore you have the right to hurt their feelings.
–Frustrated Old-Lady Namer
In a way, it is about nostalgia—or at least the effort to marry nostalgia with distinctiveness. In an age where everyone wants fresh-sounding names that are known, but not too popular, parents with a traditional bent tend to turn back three or four generations to find names that feel fresh again.
–It Takes Two
The Name Lady sees a lot of confusion about Juniors, and that's with a fairly well established tradition to follow. When it comes to the double first name, the waters are even murkier, especially for boys. The good news is that almost anything goes. The bad news is that, well, almost anything goes, so how are you supposed to decide?
Draco isn't everyone's style, but no name is! Still, even setting taste aside, I do think Draco is a problematic choice, especially for a little girl. Lots of boys' names are given to girls today, but they usually have some characteristics that make the crossover easier.