It was first created in 1097 for Walter Giffard, but became extinct in 1164 with the death of the second earl.
It may have been created again in 1164 for Richard de Clare ("Strongbow"), who died without issue in 1176.
It was created again in 1377 for Thomas of Woodstock, the youngest son of King Edward III.
The dukedom was forfeit on his attainder in 1397, but the earldom passed to his son, Humphrey, but became extinct on his death two years later.
The title was created a fourth time in 1618 for Mary Villiers for life only.