The term was applied to various peoples who had not converted to Islam at the time of colonization and was a pejorative, although some writers have reappropriated it. The term comes from the Kanuri word for pagan; the Kanuri people are predominantly Muslim.
Estimates of how many groups may be described as Kirdi vary, with estimates ranging from 26 (2007) to more than 40 (1977).
The Bata, Fali, Fata, Gemjek, Guidar, Giziga, Hurza, Kapsiki, Mada, Mafa, Massa, Matakam, Mofou, Mora, Mousgoum, Muyang, Ouldeme, Podoko, Toupouri, Vame and Zulgo are all considered Kirdi, due to their resistance to Islam. They speak Chadic and Adamawa languages.
The first mentioning of Kirdi is by Denham in 1826 (1985:145) who translates the word Kerdies as "Negroes who have never embraced the Mohammedan faith".