Fionn mac Cumhaill known in English as Finn McCool, was a mythical hunter-warrior of Irish mythology

Irish mythology

The mythology of pre-Christian Ireland did not entirely survive the conversion to Christianity, but much of it was preserved, shorn of its religious meanings, in medieval Irish literature, which represents the most extensive and best preserved of all the branch and the Historical Cycle. There are...

, occurring also in the mythologies of Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 and the Isle of Man

Isle of Man

The Isle of Man , otherwise known simply as Mann , is a self-governing British Crown Dependency, located in the Irish Sea between the islands of Great Britain and Ireland, within the British Isles. The head of state is Queen Elizabeth II, who holds the title of Lord of Mann. The Lord of Mann is...

. The stories of Fionn and his followers the Fianna

Fianna

Fianna were small, semi-independent warrior bands in Irish mythology and Scottish mythology, most notably in the stories of the Fenian Cycle, where they are led by Fionn mac Cumhaill....

, form the Fenian Cycle

Fenian Cycle

The Fenian Cycle , also referred to as the Ossianic Cycle after its narrator Oisín, is a body of prose and verse centering on the exploits of the mythical hero Fionn mac Cumhaill and his warriors the Fianna. It is one of the four major cycles of Irish mythology along with the Mythological Cycle,...

 (or Fiannaidheacht), much of it purported to be narrated by Fionn's son, the poet Oisín

Oisín

Oisín , also spelt in English Ossian or Osheen, was regarded in legend as the greatest poet of Ireland, and is a warrior of the fianna in the Ossianic or Fenian Cycle of Irish mythology...

.

"Fionn" is actually a nickname meaning "blond

Blond

Blond or blonde or fair-hair is a hair color characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors, but always has some sort of yellowish color...

", "fair", "white", or "bright". His childhood name was Deimne (icon; dʲeβ̃nʲi), literally "sureness" or "certainty", and several legends tell how he gained the nickname when his hair turned prematurely white.