The term Jackeen is believed to be derived from either Jack, a common English nickname for the names John and James, or in reference to the Union Jack, the flag of the United Kingdom. Following the Norman invasion of Ireland beginning in 1169, Dublin became the centre of the Pale, the part of Ireland directly under the control of the English government in the late Middle Ages. By the 19th century, Dublin had served as the centre for English rule in Ireland for centuries, and Dubliners were stereotyped as being heavily Anglicized and considered the most English of all the Irish. Jack is combined with the Irishdiminutive suffix "-een" (represented as -ín in Irish) meaning little, commonly found in Irish female names such as Roisín ("little Rose") and Maureen (Mairín, "little Mary"), implying that Dubliners are "little Englishmen".
Today, Jackeen is sometimes used to describe Dublin GAA players and supporters.