Recorded in many forms including O'Dennehy, O'Danagher, Danagher, Danahar, Danaher, Denny, Deeny, Dennehy, Donaher, and others, this is an Irish surname of great antiquity. It is usually to be found in County Cork, and slightly less so in County Kerry, although as Danagher, it was formerly recorded in County Limerick. However spelt the surname is believed to derive from the ancient pre 10th century Gaelic "duineachaidh", meaning pure, but it has to be said that this is not accepted by many scholars. Unfortunately todate nobody seems to have come up with a better explanation. Many, perhaps the majority of Irish surnames, originated as a nickname for the first chief of the clan, effectively the first nameholder. Some of these nicknames were "robust" to the point of physical directness, and others in the tradition of nicknames may well mean the reverse of the translation! In this case we also have confusion with the English surname Denny, to the point where overlap ensures that it is impossible to tell the difference between an English and Irish Denny. It is said that the most notable Dennehy was Sir Thomas Dennehy (1829 - 1907), a Major-General in the British army, and a governor in India, whilst Daniel Deniehy (1828-1865), born in Sydney, Australia, had just achieved prominence in the country's political system, when he died at an early age. The first known recording of the surname is probably that of Donal O' Denaghie, of Cloghlea, County Cork, an official of the church and keeper of the vestry in 1585.