Nyumba Ntobu - explain that one more time?

I've been helping Fred with the introductory aspects of the Gender Based Violence (GBV) program for our community.  They've done a ten page survey related to public awareness and acceptance of GBV, and I have been entering the surveys into a database.  It's really glamorous work. *cough*

The survey was conducted in Swahili, so I've been expanding my vocabulary while entering these surveys.  One of the phrases I was at a loss to translate, though, was "Nyumba ntobu."  It was sometimes paired with a mentioned of women marrying women, which confused me even more, because homosexuality is beyond taboo in Tanzania.  So I asked Fred, and this is what he explained.

In the villages of a certain tribal community in northwestern Tanzania, marriage is still a very transactional thing.  Early marriage is common, pulling girls as young as 13-years-old out of middle school to be married, usually to a much older man who has sufficient resources to pay a dowry.  The dowry is traditionally paid in cattle, and this transaction arranged between the girl's father and future husband is arranged without any input from the bride-to-be.

Sometimes, however, this transaction is arranged between the father of the adolescent woman and another, older woman.  This older woman is often a widow, and usually barren.  Similar to other ancient tribal cultures, a woman's retirement plan, social security, pension and retirement home is her children, but even beyond the considerations of financial security, there is a social consideration.  Barren women are not well respected in this society, so some women who have sufficient resources pay the dowry price for a young woman.  This young "wife" becomes a kind of surrogate, who is required to sleep with any men chosen by the older woman until the young girl becomes pregnant.  The younger woman may be forced to repeat this process of non-consensual sex with any number of men to produce more children who serve as grandchildren for the older woman.  There is no security, as the young woman may be sent away at any time without her children.

It's really difficult to explain all the implications of this tradition, but it definitely victimizes the young "wife" and even her children.  There are no men in the household, and it may become difficult for the two women to provide financially for the family.  One could even describe it as a kind of legalized sexual slavery, but the cultural traditions and values contributing to this practice are so deeply interwoven in the tribe that fighting against the practice seems almost hopeless.  We are discussing ways of empowering and protecting young women through the GBV program so that practices like Nyumba Ntobu may finally be stopped.