The actual word for a half-demon-half-human is "cambion", but if you're wanting something like not exactly half and half, make something up. I would suggest using etymology, though. Use words (or parts of words) from other languages. Find a unique way to describe an aspect of the character - or race of characters - like, if they're immortal, look up "mortal" in a different language, then add a prefix that means not or without, or translate "one who does not die" into Latin and use that. Obviously, the immortal was just an example, but select a defining trait of the person/people, and use a different language to make a new word. I do that all the time for naming characters or locations. Hope I've helped.
Interesting that you do that too. I did that for an Urban-Fantansy side project, where I put Dark Eldar through Arabic and got Layal Aldaar, which sounds more exotic and interesting. Though I refrain from the hybrids thing, as it is a bit overdone and scientifically virtually impossible to a very small percentage, that the odds might as well be 1/1,000,000,000, 000,000,000,000,000 of such an occurrence happening between two species that are not similar on a genetic level. So one might say that Half-Breeds, are kinda cliche in an obvious way. Why not just have a normal (whatever species) be able to have internal strife without being able to blame that half that makes them genetically different from both parent species. Good v. Bad struggles should not be on a crutch, nor should distinct advantages/disadvantages.
Lucians, as children of Lucifer. (don't necessarily have to be, it could just be what they're called.) Demifiend from the root of demigod. Or werefiend as in werewolf Hellsons or hell spawns Changeling, if you decide that faeries and demons are synonymous in your story
That explains the Nancy Pelosi reference. I was going to suggest Demi-Jumby. Or Fred. Fred seems like a nice name for a Half-Demon.
Lucifred. Beelzebubba (yes, I know). Asmodennis. Sathomas. Abaddonald. Czernoboris. Leviathaddeus. Mephistophillip. Wendigordon. Next?