The clan itself takes its name from a Niall who lived in the 13th or early 14th century and who belonged to the same dynastic family of Cowal and Knapdale as the ancestors of the Lamonts, MacEwens of Otter, Maclachlans, and the MacSweens.

If the MacNeils are indeed connected to Anrothan, then they appear to have been a junior branch of the family and were certainly overshadowed in the 13th century by the MacSweens, Lamonts and descendants of Gilchrist.

[6] His son was Neil Og Macneil who is believed to have fought for Robert the Bruce at the Battle of Bannockburn in 1314.

[7] The earliest contemporary record of the Macneils of Barra is only in 1427, when Giolla Adhamhnáin Mac Néill (typically anglicised as Gilleonan Macneil) received a charter of Barra and Boisdale, from the Lord of the Isles, following the forfeiture of the previous Lordships of Uist and Garmoran, earlier that year.

[1] Gilleonan's namesake, reckoned the twelfth chief, was one of the island lords who were tricked into meeting James V of Scotland at Portree, where they were promised safe conduct but instead were arrested and imprisoned.

[6] The treaty they signed with the English as overlords proclaimed the ancient enmity between the chiefs of the isles and the kingdom of Scotland.

[6] His son, the next chief, was denounced as a rebel by the Privy Council so many times that he was described as a "hereditary outlaw" and was known as the Turbulent or Ruari the Tatar.

[6] The king eventually arranged for his loyal vassals to extirpate and root out the chief of Clan MacNeil, whose own nephews captured him and placed him in chains.

[6] During the Scottish Civil War of the 17th century the chief of Clan MacNeil, Neil Og, was appointed as Colonel of the Horse by Charles II of England and fought at the Battle of Worcester in 1651.

[6] His grandson was Roderick Dhu the Black who received a Crown charter for all of the lands of Barra to be erected into a free barony.

[6] Upon their father's death they returned but for his Jacobite sympathies, Roderick was consigned to a prison ship, the Royal Sovereign.

[6] The clan prospered until the twenty-first chief, General Roderick Macneil, was forced to sell Barra in 1838.

[9] A recent hypothesis make Torquil, son of Niall, living in 1440, the eponym of the clan, thus totally unrelated to the Barra MacNeils.

[13] According to Moncreiffe, there is reason to believe that historically this branch was superior to the current chiefs of the Clan MacNeil.

His son John Duncan McNeill became Head of the Clan on his father's death but did not apply to matriculate his own Arms.

This consisted of 370 Catholic Barra folk (about 75 families in total) who emigrated in August to Pictou, Nova Scotia.

Immediately he began work restoring the castle, aided in part by funds from a British Government grant.

Paul Humphrey MacNeil, the elder son, in his father's lifetime renounced his allegiance to the British Crown and became an American citizen; in consequence of this his father in 1913 nominated his second son, Robert Lister MacNeil, the petitioner, to succeed him as Chief of the Clan, and assigned to him the arms pertaining to the Chief.

While clan members may wear the badge, the crest and motto within it are the heraldic property of the chief alone.

[23] The motto upon the badge is: buaidh no bas, which translates from Scottish Gaelic as "to conquer or die", or "victory or death").

A depiction of the coat of arms is painted in the Great Hall of Kisimul Castle in Castlebay, Barra, Scotland.