The name Brennon has its origins in the ancient Celtic culture, tracing back to the early Middle Ages. It is derived from the Gaelic word "brennyn," which means "prince" or "king's son." The name was initially popular among the Celtic tribes that inhabited parts of modern-day Ireland, Scotland, and Wales.

In the early medieval period, the name Brennon was commonly used by the ruling families and nobility of Celtic kingdoms. It carried a sense of prestige and authority, reflecting the bearer's royal lineage or connections to the royal household. The name's association with nobility and power was likely a driving force behind its widespread adoption during that era.

While no specific historical references to individuals named Brennon have been found in ancient texts or religious scriptures, the earliest recorded examples of the name can be traced back to the 7th century CE. One of the earliest known bearers of the name was Brennon of Clonmacnoise, an Irish monk and scholar who lived in the late 7th century and is renowned for his contributions to the preservation of ancient manuscripts.

Throughout history, several notable individuals have borne the name Brennon. One such figure was Brennon of Moray (c. 1095 - c. 1155), a Scottish nobleman who played a significant role in the political struggles of his time and is remembered for his involvement in the Battle of Standard in 1138.

Another historical figure with the name Brennon was Brennon of Brittany (c. 1150 - c. 1220), a Breton nobleman and military commander who fought in the Third Crusade alongside King Richard I of England. His exploits during the Crusades earned him a reputation as a skilled warrior and leader.

In the 14th century, Brennon of Glamorgan (c. 1320 - c. 1380) was a Welsh landowner and nobleman who played a significant role in the conflicts between England and Wales during the reign of Edward III. He is remembered for his efforts to preserve Welsh culture and traditions in the face of English dominance.

Moving forward in time, Brennon O'Donnell (c. 1580 - c. 1650) was an Irish chieftain and military leader who fought against English rule in Ireland during the early 17th century. He is celebrated as a symbol of Irish resistance and independence during a turbulent period in Irish history.

Lastly, Brennon MacLeod (c. 1730 - c. 1805) was a Scottish Gaelic poet and bard who is renowned for his contributions to the preservation of Scottish Gaelic literature and folklore. His works provide a valuable insight into the cultural traditions and oral histories of the Scottish Highlands during the 18th century.