The name Neville has a French or Norman appearance and it is true that among the Anglo-Norman invaders and settlers of the late twelfth century were one or more families called de Neville who acquired lands in south-east Leinster and are often mentioned in all relevant records. In Co. Wexford especially they were prominent in local affairs: for example, Lawrence Neville was Bishop of Ferns from 1480 to 1503 and Robert Nevyll was a notable burgess of New Ross in 1511. Thomas Nevill who claimed to come within the articles of the Treaty of Limerick was from Rathmore, Co. Kildare. There were Nevills in Clonmel in 1688. The Nevilles of counties Limerick and Cork are Gaels in disguise; during the period when it was fashionable not to be Irish they allowed the patronymic Ó Niadh to be represented in English by Neville A distinguished modern representative of the Nevilles was Dr. Neville of Blackrock College, who became Vicar-Apostolic of Zanzibar in 1913 and laboured in tropical countries with much success for 30 years. The surname Ó Niadh which means "descendant of the hero" (nia). In Connemara it takes the form Nee (sometimes spelt Knee) which is an approximately correct phonetic rendering of Niadh. In Mayo the majority of Nees have adopted the English sounding surname Needham. 

     Neville has been used as a synonym of Nevin.  It is never interchangeable with Newell. That is Ó Tnúthghail in Irish. This was a minor sept located on the border of the counties of Kildare and Meath and the name was first anglicized as O'Knowell, from where the modern Knowles come. As Newill it appeared in the Hearth Money Rolls for Co. Tyrone (1664). Three Knowles were distinguished in various branches of literature in the nineteenth century. Three Newells, too, all from the Belfast area, are noteworthy: one Edward J. Newell (1771-1798) as an informer, Alexander Newell (1824-1893) was a distinguished scientist and Hugh Newell (b.1830) an artist of repute in America.  
Source:  More Irish Families, Edward MacLysaght, Irish Academic Press, 1996.