Noob comes from newb, which comes from newbie. Some argue it comes from "nubile" but I don't personally buy that etymology. I distinctly remember "newb" followed by "noob" but that was eons ago.

Always thought it was "new" but made to sound like "boob" because it's funny.

And not related to Safire's "nattering nabobs of negativism," the originals of whom SF's Nob Hill eponymizes.

Technically “new user” I think.