Nairobi is the capital and largest city of Kenya. The name is derived from the Maasai phrase Enkare Nairobi, which translates to 'place of cool …Nairobi is the capital and largest city of Kenya. The name is derived from the Maasai phrase Enkare Nairobi, which translates to 'place of cool waters', a reference to the Nairobi River which flows through the city. The city proper had a population of 4,397,073 in the 2019 census.