Hackett (alternately Hacker, Haket, Hackert, Halkett, Ó hAicéad etc.) is a surname of Norman origin, Hacket being a common Norman personal name.
Most textbooks discussing the origin of English surnames theorize that the name Hackett originates in northern France, Malta and has Irish connections. The early history of the name is largely conjecture because of the lack of written evidence. The surname Hacker is derived from the medieval given names Hack or Hake. These English names were derived from the Old Norse name Haki, which is a cognate of the English name Hook. The Gaelic form of the name Hackett is Haicéid.
The story of the surname Hackett in England begins with Norman Conquest of 1066, when the forces of William the Conqueror defeated the native Anglo-Saxons. After his victory, William divided the countryside into estates for his main supporters as a reward for their zeal. While there were no Hacketts amongst these new Lords of the Manor, the surname became chiefly popular in the West Midlands of England upon the success of the invasion.
The Hackett name later migrated to Ireland at the time of the Anglo-Norman invasion in 1170. Members of the Hackett family accompanied Richard "Strongbow" de Clare, 2nd Earl of Pembroke during his invasion of Ireland. The Hacketts were subsequently granted estates in the modern counties of Kilkenny, Carlow and Kildare and thus became the principal holders of land and one of the most influential families in Ireland. As a result, several towns have taken the Hackett name, including Hacketstown, in County Carlow. Further, the Fiants of Henry VIII and Edward VI indicate that in the sixteenth century there were also Hacketstowns, or Ballyhackett, in Counties Dublin and Kildare.