1964, American English shortening of discotheque; sense extended by 1972 to the kind of dance music played there and the subculture of urban night-clubs built around it in the 1970s. As an adjective by 1965.
Entries linking to disco
discotheque n.
"club where recorded dance music is played," 1954 as a French word in English; nativized by 1964, from French discothèque "nightclub with recorded music for dancing" (by 1951), also "record library," borrowed 1932 from Italian discoteca "record collection, record library," coined 1927 from disco "phonograph record" (see disc) + -teca "collection" (from Latinized combining form of Greek thēkē "case, receptacle;" see theco-), probably on model of biblioteca "library."