The map above shows the distribution in the mid-1800's Griffith Valuation of the surnames Heron (green), Heran (orange), Haran (blue), Horan (yellow).
About one out of 3000 Irishmen had the surname Heron.
The Griffith Valuation lists 331 Heron (or Herron) entries. The counties shown in green are those that contained more than 20 Heron entries, and show where 2/3's of all Herons in Ireland resided. The clustering of Herons in Counties Down, Armagh, and Antrim indicates that this group probably descends from O'hErodain, a powerful sept of the Airghialla kingdom called Ui Breasail Macha. About 1000 years ago it was common in Ireland for churches and monasteries to be run by a hereditary line of laymen. These Ui Breasail Herons held such a position in the church in Armagh for a couple of hundred years. ( Rev. Woulfe gives the spelling of this same Ui Breasail sept as O'hEaradhain, and the later corrupted form O'hEarain). Of the 221 Heron entries listed in Co Armagh, Antrim, and Down, 70% percent of them were spelled as Heron, and 30% were spelled as Herron.
About one out of 20,000 Irishmen had the surname Heran.
Co Leitrim contained 80% of the 52 Herans (with variants Heeran and Hearan) listed in the Griffith Valuation. In Leitrim itself, Heran was 75%, and Heron was 17%, of the Heron variant surnames. All of the Herans were located in the southern portion of Co. Leitrim. Nothing is known of the origin of this group, or if it represents a distinct group or just a local spelling.
About one out of 4500 Irishmen had the surname Haran.
The Griffith Valuation lists 224 Harans, most of which were found along the western coast of Ireland. The counties shown in blue are those that included more than 10 Harans and show where 85% of the Harans resided. McLysaght divides this group into several distinct septs. He attributes the Harans in Clare and Connacht to the sept O'hEaghrain (Rev. Woulfe describes the O'hEaghrain as of Co Galway). Most of the Harans in Co Clare were located about 5-10 miles west of the town of Ennis (parishes of Inagh, Kilfarboy, and Kilmaley), and another group was located on the north bank of the Shannon River at Kilmurry. The Harans in Co Fermangh were known as O'hArain in 17th century documents, and were hereditary lay rulers of the church at Ballymacattagart. Harans were scattered through the whole central portion of Fermanagh. The Harans of Co Donegal were originally O'hEarain, and in the Griffith Valuation the Harans were seen to cluster just in the southern part of the county in Drumhome parish (just south of the town of Donegal). O'Hart mentions Harans in Lieney, Co Sligo and gives the Irish original name of this group as O'hUathmharain. The barony of Lieney is in the central southern portion of Sligo and is approximately the area in which the Harans are scattered in Co Sligo. Another part of this same cluster was a group of Harans just across the border in Kilbeagh Parish, Co Mayo. Co Mayo also contained another group of Harans in nearby Crossmolina Parish.
About one out of 1400 Irishmen had the surname Horan.
The Griffith Valuation lists 722 entries with the surname Horan. The counties in yellow are those that included more than 40 Horans, and show where 2/3's of the Horans in Ireland resided. Rev. Woulfe says that Horan comes from O'hUghroin sept who were a branch of the Ui Maine, and were rulers of an area in Clonrush Parish (southeast corner of Co Galway). Other sources mention that this group spread from there into Co Mayo. The Griffith Valuation shows the greatest concentration of Horans in Co Offaly (mostly in the north central part of the county), and nearly as many Horans in Co Tipperary as in Co Galway. It is not known if they spread to Offaly and Tipperary from Co Galway or if these were Horans with a separate origin not described in the ancient genealogies.