The county gets its name from the town of Wicklow, whose English name is said to derive from Buí cloch, meaning "yellow stone", perhaps a reference to the gold to be found in the Wicklow mountains. The Irish name, Cill Mhantáin, comes from Killmantan Hill in the same town. The fifth-century saint whose church was said to have stood on the hill is reputed to have been a disciple of St. Patrick. His only appearance in the records is as the subject a rebuke from the national saint for having delayed sharing food with a group of beggars, as Patrick had requested.
The county is dominated by its mountains. Wild and inaccessible for much of history, they provided a refuge for those who wished to escape from Norman and English law. The native Irish families most strongly connected with the region, the O'Byrnes and the O'Tooles, were in fact driven into Wicklow by the encroachments of the Norman newcomers on their original lands in neighbouring Co. Kildare. From their remote mountain strongholds, they posed a continual threat to the city of Dublin until the seventeenth century.
With the continuing expansion of Dublin city over the last forty years, the north of the county has effectively become part of the city suburbs.
Surnames associated with the county include Doyle, Byrne, O'Toole, Kavanagh, Lawlor and Farrar.