One of the challenges of Irish genealogy is that of identifying and locating townlands, the names and spellings of which can vary across time, and, even within the same time period, from one source to another. For a discussion of some of the difficulties, see Dr. Jane Lyons, The Townland: How to Use In Genealogy.
In the seventeenth century, English government officials also had difficulty with Irish townland names, as the following item makes clear.
This is a summary abstract, dated 6 September 1664, from the Calendar of the State Papers, Relating to Ireland Preserved in the Public Record Office, 1660-: 1663-1665 (1907), and it concerns a petition by Robert Maxwell, the Church of Ireland Bishop of Kilmore who acquired extensive landholdings in the barony of Upper Loughtee, Co. Cavan. Maxwell apparently successfully petitioned the Crown to “better secure his title and estate;” and the granting of new patents to lands he had already purchased in Dromhill and Dromellan was meant to correct some “defects in the [original] grant, some of the lands being misnamed, others not named, and others named for less than they are worth and others for more, whilst some of the lands are pretended to be concealed.” Note the attempt here (click on the image to see a larger version) to clarify the names of various townlands by indicating the various aliases by which those townland might also be known (but also note that the material in brackets [ ] was inserted by the modern  indexer):
Of particular interest to me here is the townland of origin of my Galligan ancestors: “Loghohennocke alias Loghoconnoge alias Aghnyglogh alias Agnagloype [Loughaconnick].” That’s a lot of aliases from the seventeenth century; and in the nineteenth-century records, I’ve come across a number of other variant spellings too. In the 1821 census of Kilmore, Co. Cavan, this townland is listed with four different spellling variations: Loughahonogne, Loughahonogue, Loughahunge, and Loughahunoge. In The Tithe Applotment Books, this townland appears as Lougharonog. And in Griffith’s Valuation, this townland is called Loughaconnick, which is the modern, standardized spelling — it is this spelling which has been inserted in brackets by the 1907 indexer.
Irish townland confusion: not just a problem for 21st-century family history researchers, but also a problem for 17th-century post-Cromwellian colonial overlords!