O'Heerin () is an Irish surname meaning "grandson or descendant of Uidhrin" ("little grey"). The O'Heerin clan of

Leinster Leinster ( ; or ) is one of the four provinces of Ireland, in the southeast of Ireland. The modern province comprises the ancient Kingdoms of Meath, Leinster and Osraige, which existed during Gaelic Ireland. Following the 12th-century ...

originates in the ancient

Kingdom of Uí Failghe The kingdom of Uí Fháilghe, (early spelling) or (modern spelling), () was a Gaelic-Irish kingdom which existed to 1550, the name of which (though not the territory) is preserved in the name of County Offaly (), Ireland. County Offaly was ...

corresponding to the modern

County Offaly County Offaly (; ) is a Counties of Ireland, county in Republic of Ireland, Ireland. It is part of the Eastern and Midland Region and the Provinces of Ireland, province of Leinster. It is named after the Ancient Ireland, ancient Kingdom of Uí ...

, the territory given by the second-century king

Cathair Mór Cathair Mór ("the great"), son of Feidhlimidh Fiorurghlas, a descendant of Conchobar Abradruad, was, according to Lebor Gabála Érenn, a High King of Ireland.Foras Feasa ar Éirinn, Section 40, page 259, http://www.ucc.ie/celt/published/T100054/ ...

to his eldest son Ros Failgeach. Uidhrin O'Maelmuire was an 11th-century Ui Neill chief ruling

Cenél Fearadhaigh Cenél is a surname. Notable people with the surname include: *Cenél Conaill, the name of the "kindred" or descendants of Conall Gulban, son of Niall Noígiallach defined by oral and recorded history *Cenél nEógain (in English, Cenel Eogan) is ...

, now the

barony of Clogher Clogher is a barony in County Tyrone, Northern Ireland. It is bordered by four other baronies in Northern Ireland: Omagh East to the north; Dungannon Lower to the east; Magherastephana to the south; and Tirkennedy to the south-west. It also bo ...

County Tyrone County Tyrone (; ) is one of the six counties of Northern Ireland, one of the nine counties of Ulster and one of the thirty-two traditional counties of Ireland. Its county town is Omagh. Adjoined to the south-west shore of Lough Neagh, the cou ...

in Northern Ireland. His son and grandson also ruled as chiefs, before Mac Cathmhaoil in the 12th century. It is unknown if these chiefs were related to the Leinster clan. The name next appears with the historian

Giolla na Naomh Ó hUidhrín Giolla na Naomh O hUidhrin, Irish historian and poet, died 1420. O hUidhrin is known as the author of '' Tuilleadh feasa ar Éirinn óigh'', a topographical poem of a kind with Seán Mór Ó Dubhagáin's '' Triallam timcheall na Fodla'', of whic ...

(O'Heerin) who died in 1420. His addition to

Seán Mór Ó Dubhagáin Seán Mór Ó Dubhagáin (died 1372) was an Irish Gaelic poet. Background Ó Dubhagáinn was among the first notable members of the bardic family Baile Uí Dhubhagáin (Ballyduggan), near Loughrea, County Galway. He was accorded the rank o ...

(O'Dugan)'s " Triallam timcheall na Fodla" commences with "

Tuilleadh feasa ar Éirinn óigh Tuilleadh feasa ar Éirinn óigh ("More knowledge on the entirety of Ireland") is a medieval Gaelic- Irish topographical text, composed by Giolla na Naomh Ó hUidhrín (died 1420). Overview ''Tuilleadh feasa ...'' is both a supplement and a con ...

" (More Knowledge on Sacred Ireland).

See also