The County of Brosna, for such is Offaly often called, with its 771 sq. miles ranks in area as the 18th county in Ireland. Approximately 52 miles long and 27 wide, it contains within its approximate circumstances some 1128 townlands. And the fact that each townland averages out at 406 acres suggests a lesser tendency towards subdivision than obtains in other parts of the country, a point of interest to modern students of Ireland's social history.
That the "soil of Offaly is of three kinds, limestone, bog and gravel" suggests that the Landed Gentry who arrived in with Ireland's first (but non profitable) Plantation experiment in the 1570s, busied themselves with acquiring the better limestone soils while relegating the native Irish to 'the bogs and gravels'.
But the Plantation of Laois and Offaly was nothing if not thorough. One hundred years later, Dr. William Petty, Chief Medical Officer to Cromwell's soldiery and now turned land surveyor ordered the surveyors (or terriers as they were called) under his control to "change all (townland) names from those uncouth, unintelligible (Irish) names by which their localities are known into English, the more that we might create a new era". It was thus that Offaly, like other counties also, has its goodly share of anglicised townland place names.
When viewed in general, Offaly represents a great plain. Indeed it has been said that "from Sliabh Bloom to The Hill of Allen (in neighbouring Kildare) and from Croghan Hill to An Fraoch Mor (meaning The Heath in Laois), the plain of Offaly is a tranquil as a lake".
Being full of springs as Offaly is, it is easy to appreciate many marshy areas resulted, despite the best efforts of the Brosna River to carry all waters to the Shannon. Even the word Brosna itself meaning as it does "a bundle of sticks" refers, it is thought, to decayed bundles of sticks of former alder trees which particularly suit marshy land.
The aspect of marshy or swampy land, much of it now thankfully reclaimed, is further mirrored in the ninety-three townlands which begin with the prefix Clon or Cluain. In general, Clon or Cluain means marshy land, a swamp or a meadow although some authorities (including the great O'Donovan) suggests that it means more particularly 'a raised area or field within a marsh', an oasis in fact, while the late Dr. Deirdre O'Flanagan goes a step further and offers that because early Christian settlements tended to locate on these oasis, then the term Clon or Cluain has Christian connotations.
Apart from these ninety-three Clons there are also fourteen townlands beginning with Curra or Curragh which also means 'a marsh or swamp'. The ninety-three Clons represent the largest single grouping of non anglicised Offaly townlands.
But such marshy land as the Clons and Curras naturally created small streams and rivers which needed to be crossed. These crossings we find in the sixteen townlands beginning with Atha which means 'a ford or crossing place'.
Some eighty-eight townlands, and the second largest non-anglicised grouping, begin with the word Kil or Kill which means 'a church settlement' or a possible accompanying burial place. There may be a tenuous connection this second largest grouping and the fifty-three townlands beginning with Doire (the fourth largest) Derry, or Doire, means an oak tree grove, as indeed does Durrow which also being in Offaly, was Saint Columba's favourite Irish monastery. Oak tree groves generally bespoke the pre-Christian druids who, having no symbol of their own worshipped the largest oak tree. The word 'druid' itself derives from the Irish word for oak, dair, meaning 'one who is learned from the wise old oak tree.
The third largest grouping of original Irish townlands in County Offaly is that beginning with the word 'baile'. There are fifty-five such townland prefixes. The term 'baile' originally meant "a small cluster of homesteads" since people, for one reason or another, often preferred to live as a group. And apart from a possible defensive aspect of the ancient 'baile', there are twenty four townlands containing the word 'rath' and thirteen with 'lios', both of which convey a defensive dimension.
There are nine townlands beginning with 'tulach' which means a hill, and of which An Tulach Mor (Tullamore) is a good example. Also meaning 'hill' is 'cnoc', and of these there are thirteen. Within its county boundaries, Offaly contains twenty islands on the River Shannon thirteen of which are named and seven unnamed.
The general pattern of Offaly's townland name structure fits in well with a national perspective. The six largest groupings of townland prefixes emerging from Ireland's 60,642 townlands (51,158 in the Republic) are Bailes 7,000; Kil or Cills 2,890; Clons or Cluains 1,680; Cnocs or Knocks 1,600; Lios 1,380, and Derrys 1,310.