The origin of the lip plate, according to one source, is that a neighboring tribe was stealing their women, so they tried to make their women unattractive Over time, it became a symbol of beauty to their own tribe.
Funny how that happened!
The lip is minimally cut when the female reaches adolescence, and then slowly expanded over time to accomodate a larger plate. Apparently it doesn't hurt. The plate is only removed to eat and sleep. I wonder how they talk?