I once met one of the writers of that show and he said when they were spit balling ideas for a new show they were high and thought they should create a euphemism for a brothel (that would get past the censors). Apparently they succeeded.
Uncle Joe is piano player/bouncer, the three girls initials are all "B.J." (Bobby Jo, Billie Jo and Betty Jo) and the aunt (Kate) is the madam.