Downing, Dunning
Downing, Dunning—These two names are the later anglicised forms of Downey and Dunneen, respectively, in South Munster. O'Dúnadhaigh being the Gaelic of the O'Downey sept of Co. Kerry, and O'Duinnín the Gaelic of the other sept O'Dunneen.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees