The name Donell has its roots in ancient Gaelic and Celtic origins, tracing back to the early medieval era in Ireland and Scotland. It is derived from the Irish Gaelic name Domhnall, which is a combination of the elements "domhnu" meaning "world" and "val" meaning "rule" or "ruler." Thus, the name Donell carries the meaning of "world ruler" or "ruler of the world."

This name gained popularity during the 5th and 6th centuries AD, particularly among the ruling families and nobility of Ireland and Scotland. It was a common name among the high kings and chieftains of the time, reflecting their aspirations for power and authority over their respective realms.

One of the earliest recorded instances of the name Donell can be found in the Annals of Ulster, a chronicle of medieval Irish history. The annals mention a Donell mac Muirchertaig, who was the King of Tara and High King of Ireland in the 7th century AD.

Throughout the centuries, several notable figures have borne the name Donell. One of the most famous was Donell Óg O'Brien (1572-1617), the King of Thomond and a prominent Irish leader during the Nine Years' War against English rule in Ireland. Another notable figure was Donell Dubh Ó Lochlainn (died 1064), an Irish king who ruled over the kingdom of Cenél nEógain in the 11th century.

In Scotland, the name Donell was also prominent among the Scottish Gaels. One famous bearer of the name was Donell of Islay (1455-1497), a powerful Scottish lord and chief of the Clan Donald. He was known for his role in the feuds between the Clan Donald and the Scottish Crown in the late 15th century.

Another significant figure was Donell Balloch (c. 1475-1535), a Scottish chief of the Clan Iain Abrach branch of the Clan Donald. He was a prominent figure in the turbulent political landscape of 16th century Scotland, leading his clan in various conflicts and uprisings against the Scottish Crown.

In more recent times, the name Donell has been less common, but it has still been carried on by notable individuals. One example is Donell Jones (born 1973), an American R&B singer and songwriter best known for his hit single "U Know What's Up."

While the name Donell has its roots in ancient Celtic cultures, it has transcended its historical origins and has been adopted by various cultures and communities around the world, carrying with it the rich legacy of its ancient meaning and significance.