What are the origins of the word "Daedra/Daedroth", and the Princes' names?

I get the idea the Dunmer or their Chimer ancestors had a part in the names, or were inspired by them, because Dunmer names/words such as Sheogorad and House Dagoth really bring to mind the Daedra. I'm not at all versed in languages and such, but the Tamrielic words for daedric things seem very Dunmer-ish.

Also, the answer to the previous question may cover this one, but are the Merrish and Manish names for the princes mortal creations? Or did the lords choose these for themselves and introduce themselves as such on first contact? They seem to embrace the names well enough, but I'm not sure. If I were Clavicus Vile, I would've chosen a name that didn't sound like an STD.