ladies (n.)

plural of lady (q.v.). Ladies' night (1880) originally was any event to which women were invited at an all-male club.

Every succeeding occasion is usually said to be "the best ever," but for true pleasure, comfort and genuine enjoyment it is doubtful if any occasion has been more truly "the best ever" than the ladies' night of the Paint, Oil and Varnish Club of Chicago, which was given in the Crystal ballroom of the Blackstone Hotel, Chicago, Thursday evening January 26. ["Paint, Oil and Drug Review," Feb. 1, 1911]