The name Kieran originated from the Irish Gaelic name Ciarán, which is derived from the word "ciar" meaning "black" or "dark featured". This name has its roots in ancient Celtic culture and is believed to date back to the 5th century AD.

Kieran was a popular name among early Irish saints and religious figures. One of the most notable was St. Ciarán of Saigir, who lived in the 6th century and founded the monastery of Seir-Kieran in County Offaly, Ireland. Another famous bearer of this name was St. Ciarán of Clonmacnoise, who established the important monastic school of Clonmacnoise in County Offaly in the 6th century.

In the 9th century, the Martyrology of Oengus recorded several individuals named Ciarán, indicating the name's widespread use during that era. The name also appeared in various Irish annals and historical records throughout the Middle Ages.

One of the earliest recorded examples of the name Kieran comes from the 11th century, when it was borne by Ciarán Ua Ruadhacáin, an Irish poet and historian. In the 12th century, Ciarán Ua Conchobhair was a renowned Irish scribe and scholar.

During the Medieval period, the name Kieran was also associated with prominent figures in Scotland. Kieran of Dull, a Scottish saint who lived in the 7th century, was known for founding a church in Dull, Perthshire.

Other notable individuals named Kieran throughout history include:

1. Kieran Bracken (born 1972), an English former rugby union player.
2. Kieran Culkin (born 1982), an American actor known for his roles in movies like "Succession" and "Igby Goes Down".
3. Kieran Donaghy (born 1983), an Irish former Gaelic footballer who played for Kerry.
4. Kieran Fallon (born 1965), a British former flat racing jockey.
5. Kieran Foran (born 1990), a New Zealand professional rugby league footballer.

While the name Kieran has its roots in Irish Gaelic culture, it has gained popularity worldwide and is now used in various countries and communities.