Question: What is the established year of the Irish county name whose town and largest settlement is Ennis ?

text: Etymological list of counties of Ireland
Counties

Etymological list of counties of Ireland is a list of the origins of the names of the traditional counties of Ireland, both north and south, including counties that are no longer used. Unless otherwise state, the origin of a name is from Irish.
County name Established Province Irish name Derivation
Antrim c.1400 Ulster Aontroim Named after the town of Antrim , which comes from Aontroim , meaning lone ridge . It was formerly spelt Aontruim . An older alternative name was Aontreibh meaning lone dwelling . The county was formed by merging a number of other counties in the Earldom of Ulster , notable Twescard , from the Irish Tuaisceart , North and Carrickfergus , from the Irish Carraig Fhearghais , named after Fergus Mór mac Eirc , the 6th-century king of Dál Riata
Armagh 1584/5 Ulster Ard Mhacha Named after the town of Armagh , which comes from Ard Mhacha , meaning Macha 's height . Macha was an Irish goddess associated with Ulster and Armagh , where she is said to have given birth to twins after racing a horse
Carlow 1306 Leinster Ceatharlach Named after the town of Carlow , which comes from Ceatharlach , meaning place of cattle
Cavan 1584 Ulster An Cabhán Named after the town of Cavan , which comes from An Cabhán , meaning the hollow
Clare 1565 Munster An Clár Possibly named after the town of Clarecastle , which is made up of the Irish clár ( plain ) and the English castle . Alternatively , it may come from the Norman de Clare family , who took their name in turn from the English town of Clare , which probably gets its name from the Latin clarus , clear . Before 1565 , the county was known as County Thomond ( Irish Tuamhain , from Tuadhmhumhain , meaning North Munster )
Cork c. 1200 Munster Corcaigh Named after the city of Cork , which comes from Corcach , meaning swamp
Donegal 1584/5 Ulster Dún na nGall Named after the town of Donegal , which comes from Dún na nGall , meaning stronghold of the foreigners ( i.e . the Vikings ) . An alternative name for the county is Tyrconnell or Tirconnell , after a Gaelic territory of the same name . This comes from Tír Chonaill , meaning land of Conall and is named after Conall Gulban , a son of Niall of the Nine Hostages , whose descendants founded the territory . Conall means Strong Wolf in Irish
Down early 16th century Ulster An Dún The name is derived from Dún ná Lethglas , the capital of the Dál Fiatach , now modern day Downpatrick
Dublin 1185 Leinster Áth Cliath/Duibhlinn Named after the city of Dublin , which comes from Duibhlinn , meaning black pool . Áth Cliath means hurdled ford and is the main Irish name for Dublin
Fermanagh 1584/5 Ulster Fear Manach Men of Manach . Manach may come from Old Irish Magh Eanagh , Country of the Lakes , making the whole derivation Men ( or Tribe ) of the Country of the Lakes
Galway 1565 Connacht Gaillimh Named after the city of Galway , which was named after the river Gaillimh ( meaning stoney ) . The older name was Dún Bhun na Gaillimhe , stronghold at the mouth of the Gaillimh
Kerry c. 1200 Munster Ciarraí People of Ciar . From Ciar ( black or dark brown ) , a personal name , and Raighe ( people or tribe ) . The Ciar after whom Ciarrai is named was Ciar mac Fergus , son of Fergus mac Róich , ex King of Ulster , and Queen Meabh of Connacht , both major characters of the Ulster Cycle
Kildare 1297 Leinster Cill Dara Named after the town of Kildare , which comes from Cill Dara , meaning church of the oak
Kilkenny c. 1200 Leinster Cill Chainnigh Named after the town of Kilkenny , which comes from Cill Chainnigh , meaning church of Cainnech . Saint Cainnech allegedly converted the county to Christianity in 597
Laois 1556 Leinster Laois Named after the Gaelic territory of Uí Laoighis , meaning people of Lugaid Laígne . Lugaid was granted lands after driving out forces from Munster . His name derives from Lugh . Laois was originally called Queen 's County , after Queen Mary ( Bloody Mary ) who created the county in 1556 . After the creation of the Irish Free State , it was given its current name
Leitrim 1565 Connacht Liatroim Named after the town of Leitrim , which comes from liath ( grey ) and droim ( ridge ) . Originally spelt Liathdruim
Limerick c. 1200 Munster Luimneach Named after the city of Limerick , whose Irish name possibly means bare spot . The Vikings called it Hlymrekr , which might be a transliteration of the Irish or could mean mighty noise from Old Norse hlym ( noise ) and rekr ( mighty )
Derry 1613/1585 Ulster Doire Oak wood . From Daire Coluimb Chille , The Oak-wood of Saint Columba . Columba comes from the Latin for Dove . Previously Daire Calgaich , The Oak-wood of Calgach . Calgach may have been Calgacus . The name may come from Proto-Celtic *calg-ac-os , Possessing a Blade or Possessing a Penis . The prefix London was added in 1613 , after the town had been rebuilt across the river from its previous site , in recognition of donations from the livery companies of the City of London which had enabled the English and Scottish settlers to colonise the site . This was the same time as the County was formed . There is some dispute over whether to use the name Londonderry or Derry . Most of the area for County Londonderry came from the previous County Coleraine , which was formed in 1585 . Coleraine comes from Cúil Raithin , Nook of the Ferns
Longford 1586 Leinster An Longfort Named after the town of Longford , which comes from An Longfort , meaning the port . The earlier spelling was An Longphoirt . The term was invented by Irish chroniclers to describe a Viking ship enclosure or fortress . Longford was split off from county Westmeath in 1586
Louth c. 1200 Leinster Lú Named after the village of Louth , which was named after the Irish god Lugh ( modern spelling Lú )