BEACAN was of the O'Baires, a Corca Laidhe sept, according to Bruno O'Donoghue's Parish Histories and Place Names of West Cork, in explaining the townland name Dun Beacain (Beacon's Fortress). This is anglicised Dunbeacon, and is in the Co Cork parish of Schull. Dunbeacon was the address of Teige Riogh O Coghelane, Conoghor O Cohallan, and Donogh O Cahallan, all husbandmen, who were listed among those pardoned by the government in a fiant of 1601. This fiant also lists Shane O Caghalane, shearman, of Fynaghe. That same year Dermod O Cahillane, Ballytrasnie, was listed among a pardoned group from Co Cork. Donell oge O Cahalan, Twilsk, was among a Co Roscommon group pardoned in 1582, while the following year Donell O Kahallan is among the pardoned O'Connors, O'Dullaneys, McKigans, Rochfords, Collogans and others. The earliest fiant listing one of this surname was in 1549, when Patrick Caellane was one of six pardoned labourers from Kilsaran, Co Louth.
The surname (O) Cathalane/ Culhane/Callan/Callen is from the personal name Cathalan, an early name found mostly in the south, it being a diminutive of Cathal ("strong in battle"). Leabhar na gCeart lists O hIfearnain and O Cathalain as lords of Uaithne Cliach (later the Co Limerick barony of Owney Beg). The Four Masters' Annala Rioghachta Eireann records the slaying of Maelcraeibhe O Cathalain in 902; the slaying of the son of O Cathalain in 1014; the death of Cuilen O Cathalain, lord of Uaithne Cliach in 1107; the slaying of Muircheartach O Cathalain, chief of Clann Foghartaigh in 1151, and in 1492 is registered the slaying of Philip, the son of William Maguire, by O Cathalain "in the town (or residence) of Richard, son of Belle the Knight (i mbaile Risturd mic an Ridire belle)". A footnote informs that the name O'Cathalain is common in Louth and Monaghan, where it is anglicised Callan. More Irish Families (Mac Lysaght) says that the eponymous ancestor of the Oriel sept was Cathalan, King of Farney, who was slain in 1028. A third distinct sept of O Cathalain was to be found in what is now Co Roscommon in early mediaeval times, but the name is rare there today.
In the 14th century the O Cathalain of Uaithne Cliach were dispossessed by the Leinster family O Maoilriain, later abbreviated to O Riain, anglice (O)Ryan. The only anglicised form of O Cathalain that is found in the 1659 Census is Callan, being among the principal Irish names in the Co Dublin baronies of Balrothery and Rathdown; in the Co Louth baronies of Louth, Dundalk, Ferrard and Ardee, and in the Co Meath barony of Screen. Owners of Land of One Acre and Upwards (1876) listed nobody bearing the name Cahalane, but Michael and Margaret Culhane, Glin, Co Limerick, had 13 and 12 acres respectively. In Co Louth the Callans had holdings of 1,287 and 391 acres; in Co Monaghan holdings of 132 and 129 acres, and one each of 43 and 84 in Cos Cavan and Down.
Current telephone directories list 334 Callans, of which 207 are in the 04 area; 151 Culhanes, of which 95 are in the 06 area, 106 Cahalanes, of which 80 are in the 02 area.
O Cathalain had a variety of anglicised spellings, and occasionally had K as its initial letter. Lord Orrery, in a letter of July 1st, 1735 to one Mr Ferreby writes: "A Murrain on Counsellor Kalaan that will not suffer me to indulge myself half enough in his Company." This man was one of the most noted lawyers in Ireland, according to a footnote. In this letter, Orrery bewails the suddenness of his departure from England, stating that his "Counsel, learned in the Law (which is a genteel Phrase for a parcel of PickPockets) declare it absolutely necessary for their Profit and my Plague that I should travel Quixot-like over Ireland in search of certain Lands and Tenements now in possession of some Hibernian Giants." After his reference to Counsellor Kalaan, he adds: "Lawyers are as great Enemies to Freedom and Pleasure as Monks and Hermits are: Prose, and the dullest Prose, is their profit; They abhor Poetry and all its Professors ... "
Daniel Cohalan (1859-1952) was an outspoken critic during the War of Independence, while American-born Judge Daniel Cohalan (1865-1946) played an influential role in Irish-American societies, and an important role in New York in the preparation of the 1916 Rising.