genealogies of the families
MacCOY, (MacCooey) MacCoy is a fairly common name in Ireland: it is chiefly to be found in Ulster on both sides of the border (Armagh-Monaghan area) with a sprinkling in Cork and Limerick. It is a variant of MacKay, in Irish MacAodha (i.e. son of Hugh). The MacKays and MacCoys are not by origin Irish in the usual sense of the word, since they came to Ireland as gallowglasses in the wake of the MacDonnells, their home territory being the southern isles of Scotland (Islay etc.) though the Gaelic settlers in Alba came, no doubt, originally from Ireland. Like the MacDonnells some of the MacCoys went south, hence the families in Munster mentioned above. The name has not been very noteworthy in the political and cultural history of Ireland, but in this connexion Rev. Edward MacCoy (1839-1872), Gaelic writer, may be cited. Sir Frederick MacCoy (1823-1899), the Dublin-born naturist, is best known for his work in that field in Australia. Several MacCoys have been prominent in America, but these do not appear to have had any connexion with Ireland. Less distinguished, if equally prominent, were the MacCoys of the gang so called. The origin of the expression "the rale MacCoy" is in dispute: some authorities state that it is a corruption of the Portugese word Macao (i.e. heroin from Macao); others connect it with an individual viz. the boxer "Kid" MacCoy, who was somewhat of a dandy. The Ulster Gaelic poet Art MacCoy (c. 1715-1774), was also known as MacCooey in English, his name in Irish being Mac Cobhthaigh.
Source: Irish Families by Edward MacLysaght MA, D Litt, MRIA - Irish Academic Press 1991