Irish Surnames came into use beginning in the 10th and 11th centuries. Our ancestors briefly began using the Uá hAinninn spelling but soon settled on the preferred Irish language spelling of our Sept name as -- Ó hAnnáin. The use of the "Ó" (meaning 'grandson of') in Irish surnames was indigenous only to Ireland. Much later came the various anglicised spellings - minus the Ó - that we know today.

Dropping the "Ó" was something most Irish celtic families had to do after the English Penal Laws (1691-1829) issued by Parliament, outlawed the Irish spelling of surnames. This took place at the same time the Irish language was outlawed. Some clans, however, were able to continue the use of the indigenous "O" (O'Brien, O'Connor, O'Neill) in their names because of their "Earl" status with the Crown. However, they too had to anglicise their surnames from their original Irish spellings (Ó Briain, Ó Conchobhair, Ó Néill).

Along with thousands of other Irish sept surnames, Hannon/Hannans were not able to keep the indigenous Irish "Ó" in their surname if they wanted to find work and feed their families. The Irish spelling, Ó hAnnáin, is now rarely seen (though in modern times some families are changing their names back to the original ancient spelling).

The Property Valuation Surveys of 1848 through 1864 tell us there were 377 Hannon Households and 391 Hannan Households spread across 27 counties in Ireland: Limerick (129), Sligo (86), Cork (80), Galway (66), Roscommon (46), Antrim (41), Mayo (39), Kildare (37), Clare (35), Tipperary (27), Offaly (23), Dublin (22), Westmeath (22), Kerry (17), Leitrim (15), Meath (15), Waterford (13), Tyrone (11), Wexford (8), Armagh (7), Carlow (6), Wicklow (6), Down (6), Donegal (5), Derry (3), Cavan (2), and Louth (1) [Source: Irish Times.Com] (absent in Cos. Kilkenny, Laois, Longford, Monaghan, and Fermanagh)

Were these all of the Hannon/Hannan households in Ireland at the time? The answer is probably 'no'. During the period of the Penal Laws, Irish Catholics were forbidden to own property. Not till after 1829 were they able to own property and that property quite often was given to them by landlords they had worked for over a long period of time. Presumably not all Hannon/Hannans were given property by their landlords - so their existence would not have been counted in the Property Valuation Surveys.

By 1890, the surname was principally found in Counties Limerick, Sligo, Cork, Galway and Roscommon. These are 5 counties in the provinces of Connacht and Munster. The estimated number of bearers of the Hannon name at the time in the Emerald Isle -- was 4,260.

Also in 1890, the Birth Index shows that 40 Hannon births took place in Connacht, while 28 Hannon births took place in Munster. (Hannan birth numbers may have been included under the 'Hannon' spelling)

In the 1900 US Census - "Hannon" was the 2,792nd most numerous surname, with an estimated 11,000 living in America. That meant that more Hannon descendents were living in America in the year 1900 - than in Ireland.