I think this is very interesting:

"Potions teacher and head of Slytherin house. Rival of James, Remus, Sirius, and Peter.

"Severus" is Latin for "stern" or "harsh". There was a Roman emperor named Lucius Severus. Supposedly, Jo made the Potions master the "enemy" because she didn't like a Chemistry teacher she once had.

"Snape" is a small town Jo once visited. According to Blaise and the OED: I was delighted to find that the word "snape" actually has a meaning beyond simply being a place-name (in that context it means a boggy patch of ground). To snape someone means to rebuke or hurt them, and a snape is a rebuke. It's an almost obsolete English dialectical word from the Norse, if anyone cares."

I think this fits his description perfectly!