the.com/nightclub

means A commercial venue that opens at night offering music, dancing, and drinks to paying patrons.

from Straightforward compound of 'night' and 'club' — the latter from the older sense of 'club' meaning a group of people who band together (originally from the idea of 'clubbing together,' pooling money or effort), which by the 1800s had come to mean the physical premises such a group used. 'Night club' emerged in that century for establishments catering to after-hours entertainment, often skirting daytime licensing laws — the name simply announcing the hour rather than hiding any secret.