BBI stands for Building Bridges Initiative. BBI origin was when President Uhuru Kenyatta and Opposition leader Raila Odinga decided to shake hands and end their political confrontation that had led to instability in the country after the contested 2017 presidential elections.
Thereafter, the two agreed on a plan to amend the constitution to end the cycle of political violence in Kenya after every presidential election. The constitutional amendment drive is what is referred to as the BBI referendum.
Learn more about BBI Referendum and download the BBI constitutional amendment document: https://kenyayote.com/bbi-report-pdf-and-summary-building-bridges-initiative-kenya/