I was just about to say that too. Ditzy is clearly an insult, while Derpy Hooves sounds a bit like somepony who would wow you on a dance floor. Kinda like "Fancy Hooves."
I'unno, a friend of mine has been known to object, on more than one occasion, on the grounds that the word "derpy" "comes from ****ing South Park". Except without the asterisks.
Ever since, I've tried to avoid naming that pegasus around her at all.
Level 4 Bibliophile/Level 3 Bard, working toward the Bibliomancer Prestige Class
Brandon Sanderson recommender... In The Playground!