sasunarufan02 asks, "How do the fae go about naming their pure-blood kids/changeling kids?"
Fae naming! Hooray! One of my favorite "oh sweet Great Pumpkin she's talking about it again make her stop topics!"
Let's face it: when the majority of your population can reasonably expect to live for centuries, if not forever, names like "John" and "Mary" stop working for you real, real fast. There's not enough turn-over, and nicknames only go so far. Also, you're going to have an influx of changelings whose mortal parents insisted on "John" and "Mary," which puts even more pressure on the long-lived to avoid common names. Plus, nothing will ever really go out of fashion, since names don't "age out" when the people who have them insist on continuing to walk around and do stuff, rather than politely dying and allowing trendy new names to come into fashion. So what do you get?
You get theme naming.
In Faerie, it's considered insulting to name someone directly after someone else, as it implies either that you're hoping to replace them, or that you expect them to die soon. You can, however, give names to honor or acknowledge specific people. So October, for example, is named partially to honor September Torquill, who was a close friend of Amandine's. October comes after September. September herself was named to honor her father, Septimus, as were her two brothers, Simon and Sylvester. It's a very "S"-y family. (Yes, there are reasons that October was named after a Torquill, no, I won't go into them yet, no, Sylvester is not her father.)
Another example of same-letter naming is the Lorden family, where Patrick and Dianda named their sons Peter and Dean. Both of these are relatively common names, but the Undersea is distinct enough from the land that they have a wider range of names they haven't used yet. The mermaids could give a shit if there's already a Cu Sidhe named "Bob."
Back to October: her name is part of a chain of month names that honor by meaning, not by sound. So September named her own daughter "January," in part to honor the baby's Tylwyth Teg father (since they're often associated with ice and the winter in this setting), and in part after herself, at the urging of her husband. When January had a daughter of her own, she named her "April," both in honor of her mother, and as an acknowledgment to the Chinese holiday of Qingming, to honor her wife. (As a Dryad, April didn't really have a name. So naming her was appropriate and necessary.)
As for Toby's daughter, Gillian...I have had exactly one person email to ask if I was aware that "Gillian" is a form of "Julius." Yes. Yes, I was. While Toby didn't want to outright name her daughter "July," or even "Julia," the fae tendency toward referential naming is very strong, and so she found a name that could be traced back to "July" without actually being "July." Because old habits are hard to break.
Fae families will literally have children named "Antigone" growing up next to children named "Tom," and maybe children named "Duvet," because they like the sound of those names, and they fit into some obscure set of familial naming chains. Oh, and a lot of fae change their names as they age, either to achieve a fresh start, or for social reasons (Princes of Cats change their names when they become Kings, for example). This can trigger a whole new set of referential names.
And now you know.