That song must be 50 years old! It is nothing we ever said nor that I ever heard. Of course ,I heard the song many times and probably never listened to the words. It was just a creative expression in a song, just like we would never say to put any kind of rags on unless kidding around. Poetic license! It is quite a happy expression "put your glad clothes on..." It creates a picture in your mind of having a blast at a party. I like it . However it is not used.