[Mithadan]

"Magic," to the Elves was not something exceptional. Rather, it was something inherent in their nature; the way they manifest their power and skills. While not clear, it seems that Elven "magic" was neither good or bad, but rather part of their nature. Of course, the manner that the "magic" is used may determine whether it is evil or good in effect.

Dwimmer, as a prefix, seems to carry with it negative connotations. Not unlike the distinction between a sorcerer and a wizard. I am no philologist, but dwimmer, as used by Tolkien, is a modifier, almost like an adjective, that may best translate to "sorcerous."