Septs: May, Mea, Mawe, Mayo, Mee, Mea, O´Miey.

The Gaelic-Irish sept of Ó Miadhaigh, first anglicized as O'Miey and later as Mee, Mea and even May, was located in Teffia where the place-name Clonyveey is a memorial of it. A member of it was notorious at an early date when Gilla-gan-máthair Ó Miadhaigh struck off the head of Hugh de Lacy in 1186. As was the case with most of the Irish septs in that area, they were dispossessed by Norman families and remained in their homeland in humble positions. Some moved north-westwards: Conor O'Miey was one of the followers of Rory O'Donnell in Tirconnell, and today they are mostly found in Sligo and neighbouring counties, where Mea and Mee are the usual modern forms of the name. Mee is occasionally found as an abbreviation of MacNamee. The Mays who appeared often in the Co. Tipperary Hearth Money Rolls of 1666 were Mac Mághe. The pronunciation of this is not far from MacMawe, and Mawe is a synonym of May in use in the part of the country associated with the MacMawes. Mac Máighe is an abbreviation of Mac Máigheog. They were sometimes called MacMawe-Condon in English. Barnard May and David May were sovereigns of New Ross in 1287 and 1290; and in 1305 a John Mey was an Inquisition juror at Ardmoyle, Co. Tipperary. Richard May was a tenant of cathedral lands in Co. Waterford in 1427. Possibly not a MacMay for many of the Mays are of English origin. May is an indigenous English surname and it is also Anglo-Norman. As early as 1210 Ralph de May was proprietor of lands at Ratoath. John Mey was Archbishop of Armagh from 1444 to 1456; Sir Algernon May acquired much land in Co. Kilkenny and appeared in the Kilkenny Book of Survey and Distribution as a new proprietor in the baronies of Ida and Iverk; and many of immigrant stock, are often met with in the records of the civic and commercial life of the city of Dublin from 1500 onwards. George Augustus May (1815-1892), a Belfastman, was a distinguished Irish judge. MacMayo, also abbreviated to Mayo, appeared as a surname in the Book of Survey and Distribution for Co. Mayo and a few years earlier (1647) in the Ormond MSS. an army officer described both as Mayo and May is found. There are at least three different origins for the name May in Ireland.

The name May in Ireland is derived from the native Gaelic O'Miadhaigh Sept that was located in County Westmeath and is taken from a Gaelic word that translates as 'honourable'. Mea and Mawe are variant spellings. May was also introduced into Ulster Province by settlers from England, especially during the seventeenth century.

The name Mayo in Ireland is derived from the native Gaelic MacMaighiu sept who also anglicized their name as MacMawe, Mahew and Mayhew. This Gaelic name is taken from the Norse first name Maheu, later changed to Matthew.