ditzy (adj.)

also ditsy, "stupid, scatterbrained" (especially of women), by 1973, U.S. slang, of unknown origin; one guess [OED] is that it is a corruption of earlier African-American vernacular dicty (1926) "conceited, snobbish," also of unknown origin, but the sense is very difficult to reconcile. Could dizzy be involved? The noun ditz (1982) appears to be a back-formation.