Neil

Neil is a masculine name of Irish origin. The name is an Anglicisation of the Irish "Niall" which is of disputed derivation. The Irish name may be derived from words meaning "cloud", "passionate", or "champion". As a surname, Neil is traced back to Niall of the Nine Hostages who was an Irish king and eponymous ancestor of the Uí Néill and MacNeil kindred. Most authorities cite the meaning of Neil in the context of a surname as meaning "champion".
Origins.
The Gaelic name was adopted by the Vikings and taken to Iceland as "Njáll" (see Nigel). From Iceland it went via Norway, Denmark, and Normandy to England. The name also entered Northern England and Yorkshire directly from Ireland, and from Norwegian settlers. "Neal" or "Neall" is the Middle English form of "Nigel".
As a first name, during the Middle Ages, the Gaelic name was popular in Ireland and Scotland. During the 20th century "Neil" began to be used in England and North America, and grew in popularity throughout the English-speaking world; however, in England, it has recently been eclipsed by the Gaelic form.
The surname "Neil" is a reduced form of the surname "McNeil" (from the Gaelic "Mac Néill", "son of "Niall""), or variant form the surname of Neill (from the Irish "Ó Néill" and Mac Néill or the Scottish Gaelic "Mac Néill", meaning "descendant of "Niall"" and "son of "Niall"".
The name passed from Ireland to Scotland where it had the "Mc/Mac" prefix a prefix that already existed in the Irish surname such as Lóegaire mac Néill. Some Scottish McNeill's returned to Ireland in the 14th century and are associated with "MacNeill", "MacGreal", "MacReill", and "Mag Reil" surnames.
The Manx version of the name is "Kneal" (1598), "Kneale" (1655), or "Kneel" (1636). It evolved from McNelle (1408) and MacNeyll (1430) becoming Kneal by 1598.
Variants.
Variants of the given name include: "Neale" and "Neal".
The table below sets out the various surnames derived from "Niall and Nial"