A bororiet (pl., bororiosiek) was a kind of geographic division of the traditional society of the Nandi people of Kenya.
Each bororiet was made up of kokwotinwek (sing., kokwet) which were groups of homesteads within the same locality, roughly equal to a hamlet but smaller than a village.
These "tribes" and the territory they occupied were called *e:m.[2] The Kokwet concept and division also appears to be of ancient heritage found as it is among the other Kalenjin groups, including the Pokot society whose heritage is estimated to have separated from the main Kalenjin society more than a millennium ago.
The concept of the bororiet, however, was unique to the Nandi and is presumed to have begun sometime after the settlement in Aldai by Kakipoch and his followers.
For example, if one's family lived in one bororiet but was haunted by repetitive deaths that pointed to a curse, a ceremony reminiscent of 'Kap Kiyai' was performed to allow the family to change their bororiet by "crossing a river" in the context of ma yaitoos miat aino which literally means that death does not cross a river (body of water).