Webster's Collegiate also gives the date 1969.
Some sources credit a DJ, Gus Gossert, with coining the term in the 1970's.
The syllables first appeared on wax in 1954; a group called Carlyle Dundee and the Dundees (see www.electricearl.com/dws/origin.html). Other record citations are given at this website.

Joe Fineman, would you please reproduce the quote from the OED? My 1985 supplement doesn't have it or I can't find it. Webster's just gives the date 1969 but not the quote.