genealogies of the families
MacKenna is one of the few names from which the old Gaelic prefixes of Mac and O were not generally dropped in the dark period of the eighteenth and nineteenth centuries.
Though almost always written MacKenna, in the spoken language Kenna is quite common and in some places, notably Clare and Kerry, the emphasis is on the final A, with the result that births have been from time to time registered under many synonyms - such as Kennagh, Ginnaw and even Gna.
These forms are peculiar to Co. Kerry. By origin, however, the MacKennas do not belong to Munster. They are a branch of the southern Ui Neill but, nevertheless, they are seated in south Leinster, their territory being Truagh (the modern barony of Trough in the northern part of Co. Monaghan).
A branch of this sept settled in the parish of Maghera, Co. Down in the seventeenth century. The MacKennas, though "lords of Truagh", were not prominent in mediaeval times. O'Dugan in the "Topographical Poems" says that they were originally Meathmen before they settled in Truagh.
In our modem history nearly all of MacKennas of note have made their name in the field of literature. Niall MacKenna (b. c. 1710) was a Gaelic poet and harper; Theobald MacKenna (d. 1808), secretary of the Catholic Committee in 1791, was a prolific pamphleteer; Andrew MacKenna (1833-1872), was a leading editor and writer in Belfast; Stephen MacKenna (I837-1883), was a novelist; better known as a novelist is another Stephen MacKenna (b. 1888), while a third Stephen MacKenna (1872-1934), was translator of Plotinus and an Irish language enthusiast; Father Lambert MacKenna, S.J. (1870-1956), known for his English-Irish Dictionary, has many Gaelic language publications to his credit.
Nearly all of these were of families belonging to the country around Trough, as also was General John MacKenna (1771-1814), who, after a period of service in the Spanish army, joined Bernard O'Higgins, the "Liberator of Chile", and became an outstanding figure in South America. Patrick MacKenna (b. c. 1765), of Maghera, was an active associate of Wolfe Tone and Napper Tandy: he became a successful shipbuilder at Boulogne. Father Charles MacKenna, P.P. of Donagh, which is in the barony of Trough, was chaplain to the Irish Brigade at Fontenoy in 1745. At the present time probably the best known bearer of the name is Siobhan MacKenna, the Irish actress.
Source:Irish Families by Edward MacLysaght MA, D Litt, MRIA - Irish Academic Press 1991