In the Surma tribe of South Ethiopia, many women have a lip plate as shown here. This woman has an impressively large lip plate - but she did not start with this. When she was an adolescent, an incision was made just beneath her lower lip and a tiny gage was put in. Over time she has stretched her lip and built up to the size you see here.
There is no definitive answer as to how this tradition commenced. Some in the tribe assert that it was to discourage slave traders from kidnapping them and selling them abroad.
Among the Surma youth, this practice is slowly dwindling. One girl I spoke to said that in school they told her that it was bad. This alone ended up convincing her not to do it.
Another fun fact: when women fight each other, the dangling lip is often one of the first targets for attack. Ouch!