Some Randomly-Asked Questions [because they can't yet be frequently-asked]:

Okay, so Frith is...?

She's a Chiropteran Human.

What are Chiropterans [Avians, Fae, etc.]?

Chiropterans are the dragon- or bat-winged people, Avians are the bird-winged ones, Fae are the Insectoid-winged ones, and Aquatics are the Fish-Winged [or perhaps you'd prefer "finned"] ones. The wings are not fully-corporeal which is why the inhabitants of this world who can't see wings don't notice them at all.

Why are they called humans if they're really not? And how did they come up with the word "human" just like we did??

"Human" is the closest English translation from their language. They're quite obviously not, but to call them what they call themselves would hold no meaning to a human audience... You can't make a story too inaccessible or people won't take emotional stock in it and just won't care what happens in the story. As for the first question, Frith and others like her -appear- human, because most people on that planet are incapable of seeing wings. This is due to a massive war much earlier in the history of the planet. [See Background Information for more on that.]