The Online Etymology Dictionary said it was unknown. However, it also says that one of the meanings of dis, as in disrespect, was originally:
short for disconnected in the telephone sense and used figuratively in slang to mean "weak in the head"
I'm curious if ditzy may have come from dis.
Any thoughts on the matter?
Best Answer
From Dr. William Long:
Here's the OED's 1976 earliest citation from Texas Monthly:
Here's an antecedent from 1974's Myra & Gore by John Mitzel:
Here's another from a 1974 New York Theatre Critics' Reviews:
Finally, here's an antecedent for the OED's alternate spelling ditsy, from 1973's They've Shot the President's Daughter! by Edward Stewart: