Shortened from
迪斯科厅 (dísīkē tīng), itself a transliteration of 'disco' + 'hall'.
迪厅 carries strong 1990s nostalgia in mainland China — when economic reform first allowed nightclubs. By the 2000s younger speakers shifted to
夜店 (yèdiàn) or
酒吧 (jiǔbā);
迪厅 now sounds slightly dated.