Gikuyu or Kikuyu (Gikuyu: Gĩkũyũ, pronounced [ɣēkōjó]) is a language in the Central Bantu branch of the Niger-Congo family spoken primarily by the Kikuyu people of Kenya. Numbering about 5,3 million (22% of Kenya's population), they are the largest ethnic group in Kenya. Gikuyu is spoken in the area between Nyeri and Nairobi. Gikuyu is one of the five languages of the Thagichu subgroup of the Bantu languages, which stretches from Kenya to Tanzania. The Gikuyu people usually identify their lands by the surrounding mountain ranges in Central Kenya which they call Kirinyaga.
source
wikipedia.org,
cnrs.fr &
ethnologue.com