Ammon Shea has supplied evidence from December 1963.
Was a disco a dress before it was a nightclub? That’s the surprising implication of the evidence OED researchers have uncovered while revising the entry for disco n. The earliest quotations our editors have found for the word, which is shortened from discotheque, mean ‘a type of short sleeveless dress’ (such as one might wear to a discotheque) and date from July 1964.
1964 Salt Lake Tribune 12 July 4w The ‘disco’ to the fashion-hep means a short, bare-topped dress whose main ingredient is that it must swing.
It isn’t until the September 1964 issue of Playboy that we see disco meaning ‘a nightclub’ (though references to disco dancing are found as early as August):
1964 Playboy Sept. 56/2 Los Angeles has emerged with the biggest and brassiest of the discos.
This evidence all suggests that the word disco emerged in the United States in the summer of 1964. Can you help us resolve whether the ‘nightclub’ meaning is actually the earliest one? Publications about nightlife in the 1960s might be a good place to start looking.
OED editor Fiona McPherson explains this appeal below:
Posted by OED_Editor on 30 September 2012 19.29