Professor Binns
"My subject is History of Magic. I deal with facts, not myths and legends."
     -- Professor Binns

History of Magic teacher, the only professor at Hogwarts who is a ghost. Binns enters the classroom through the blackboard. He is ancient and shriveled in appearance and is the semi-transparent, pearly-white color of a typical ghost. The story is that Binns was so old that one morning, upon waking up in front of the staff room fire, he simply went off to class, leaving his body behind. His routine has not varied a whit since.

Binns' classes are remarkable only for their utter dreariness. He reads through endless details of goblin uprisings and other events "in a flat drone like an old vacuum cleaner" which puts everyone into a stupor.

Another name which is really a subtle bit of wordplay is Professor Binns. I imagine him wearing very  thick lenses - "bins" (from binoculars) is a slang term for spectacles.
     --Morag Traynor

Binns
hair: pearly gray
eyes: pearly gray
voice: dry, reedy, and wheezy; tends to drone on and on
distinguishing features: well, he's dead
age: so old that he died of old age
field: History of Magic
interests: cold, hard, verifiable facts