The meaning of Beithne (or Meithne, the form found in the earliest evidence) is unclear.

1450c. ‘Cill Meithne’ is the earliest recorded form of the name, in a bardic poem preserved in the Book of Lismore (this may have been pronounced as Cill Mheithne, as lenited m (‘m séimhithe’) was not marked in writing in the older Irish language, at least in Old- and Middle-Irish). Coill “wood” instead of cill “church” is already evident in Irish sources form the late 15th century. Much of the relevant historical evidence is included in Logainmneacha na hÉireann I (1990), edited by Art Ó Maolfabhail). Another example of the placename in poetry appeared in a collection called Bardic Miscellany (2010), edited by D. McManus and E. Ó Raghallaigh, where it is recorded as ‘a cCoill Mheithne’ (“in Coill Mheithne”). The example from Annála Ríoghachta Éireann (the ‘Annals of the Four Masters’) under the year 1502, ‘Choille Beithne’ (genitive form), shows that the development Cill/Coill Mheithne to Coill Bheithne (with initial Bh-) had already occurred by the time this collection of annals was compiled in the early 17th century at any rate. Lenited m- and b- became indistinguishable in spoken Irish.

John O’Donovan wrote of this name in 1840 in one of the well-known Ordnance Survey letters, dealing with the parish of Kilbehenny; he based the Irish form of the name on the aforementioned entry from the Annals of the Four Masters — which he wrongly transcribed as ‘Cill Beithne’ — and offered the following translation, ‘Cill Beithne probably signifies the Church of the Birch Trees’. P.W. Joyce, in the Origin and History of Irish Names of Places, vol. I (1869), also based his translation of the name, “birch-wood”, on the entry in the Annals of the Four Masters, ‘Coill-beithne’, and went on to state that ‘this interpretation is corroborated by the fact that the place is situated at a point where the little river Behanagh (‘birch-producing river’) joins the Funshion. The river Behanagh is located by a townland of the same name. It derives from Beithíneach “place of small birch trees”, rather than Joyce’s interpretation. As there isn’t any word in Irish * beithne meaning “birch trees”, the proximity of Beithíneach to Coill Bheithne seems to be simply fortuitous.

Another interesting conjecture on the origin of the name is provided by Pádraig Ó Riain in A Dictionary of Irish Saints (2011), under the entry Meithean. There were two related female saints of this name, according to the Irish genealogies of Saints, Meithean Chaol and Meithean Fhionn, and St. Fionnchú of Brigown (near Mitchelstown) was another member of the same family. Therefore it is possible, as Ó Riain has surmised, that ‘the name Kilbeheny, if derived from Cill rather than Coill Bheithne (or Mheithne) may recall Meithean’.

[PÓC]