Frauenzimmer. Help!

In The Interpretation of Dreams Freud says a room (zimmer) in a dream means woman (Frauenzimmer). The translator says "Frauenzimmer," literally "woman's apartment," is also a "slightly derogatory term for woman." But does it mean "slut"? The two german-speaking professors I've talked to said no. In the 18th c. it was simply a term for "jeune fille." In 19th c. Vienna it was apparently a term for the woman-servant employed in the bourgeois household. But there is a book of photos out right now called Frauenzimmer: Brothels in Germany:

What does this word mean? And where can I read more about it?