Nairobi – ‘Naii’ – is the crucible and birthplace of Sheng, the capital city of Kenya from where – including the metropolitan area – about 60 per cent of the country's economic output is produced (KNBS, 2015), and from where many influences (fashion, style, language) radiate to other parts of the country. It is one of the fastest growing cities in Africa of about 4 million, a complex, multiethnic population with vast economic disparities. Nairobi is typical of cities, with problems, crime and insecurity, but it is also a place of opportunity for achievement in life, a complex, multilingual ‘linguistic ecology’ (Bokamba 1989). Nairobi is one of the 47 counties of Kenya, consisting of Starehe, Dagoretti, Lang’ata, Kamukunji, Makadara, Kasarani, Embakasi, Njiru, and Westlands sub-counties. Nairobi River and its tributaries run through the city under severe threat from over-construction, which encroaches their banks, and garbage pollution. These rivers have names: Ruaraka (Rũĩ Rwa Aka or ‘women's river’ in Gikuyu), Kasarani (Gathaarainĩ) and Kitisuru (Gitathurũ), Mathare and Karura.

These rivers also mark natural boundaries between Nairobi and its neighbouring counties: River Kasarani marks the boundary between Nairobi and Kiambu, while River Mbagathi (< Maasai, Em-bagas – Mol 1996) runs through the boundaries with Kajiado county to the south, and with Machakos county to the east. These are large and densely populated counties, whose indigenous populations mainly speak Gikuyu, Kamba, and Maasai languages. Therefore they have a greater influence on the language, culture and society of Nairobi. For example, the name of both the river and the city is in Maasai language, and the original names of the five tributaries of Nairobi River are Gikuyu (in parenthesis above), adapted to Swahili except the last two whose pronunciation presents no issues to the Swahili speaker.

The colonial city

‘Nairobi’ is a Maasai language place name meaning ‘[that] which is cold’, or in its full version, -are-na-irobi or ‘the stream which is cold, the Nairobi river’ (Mol 1996). The town of Nairobi started in 1899 as a railway depot on the Kenya–Uganda Railway where British contractors decided to establish a base before heading west towards the escarpment. It was a convenient stopping place 300 miles from the Indian Ocean before Uganda to the west, at Mile 317 of the Mombasa to Lake Victoria railway line.