Gusiilaay is the language principally spoken in the town of Thionck-Essyl, in the Department of Bignona in the region of Ziguinchor in the Casamance, Senegal. The town has a population of about 15,000 people and there are many more people who have their roots in Thionck-Essyl who live in major cities in Senegal and the Gambia, particularly Ziguinchor and Dakar, and of course some have moved further overseas.
Gusiilaay is a member of the Jola language family. While there are different theories concerning the origins of the people of Thionck-Essyl, it seems likely that they trace their roots to the village of Essil in the Bandial region (also known as the Mof Avi). Around 500 years ago some families moved to the North bank of the river Casamance and settled near the current location of Thionck-Essyl. This is why the language is linguistically similar to Bandial (bqj) but has a large number of lexical differences, presumably of Bainouk origin. The vocabulary of the language has been further influenced by the surrounding Jola Fonyi (Buluf), and by Mandinka, Wolof and French.
