The name Keira is derived from the ancient Irish Gaelic word "ciar," which means "black" or "dark-featured." It is believed to have originated in Ireland and Scotland in the early Middle Ages, around the 5th or 6th century CE.

Keira was a relatively uncommon name in ancient times, but it did appear in some historical records and texts. One of the earliest known references to the name is in the Irish Annals, which recorded the death of a woman named Ciar in the year 580 CE.

In the 9th century, a Scottish noblewoman named Keira was mentioned in the chronicles of the Kingdom of Strathclyde. She was said to be a descendant of the royal Gaelic line and played a role in the political affairs of the region.

During the High Middle Ages, from the 11th to 13th centuries, the name Keira was occasionally used by noble families in Ireland and Scotland. One notable example is Keira of Moray, a 12th-century Scottish princess who was a patron of the arts and literature.

In the 16th century, a woman named Keira O'Neill was a member of the powerful O'Neill clan in Ulster, Ireland. She was known for her involvement in the conflicts between the English and the Irish during the Tudor conquest of Ireland.

Another historical figure with the name Keira was Keira MacLeod, a 17th-century Scottish noblewoman from the Isle of Skye. She was renowned for her leadership and bravery during the Jacobite risings of the late 17th and early 18th centuries.

While the name Keira was not extremely common throughout history, it has been used consistently in Ireland, Scotland, and other parts of the British Isles over the centuries. Its dark and mysterious origins have contributed to its enduring appeal and cultural significance.