The Birth Index of 1890 gives the Cogan family centred in Co. Cork. Cogane is given as a principal name of Cork in 1659. The family name has been traditionally linked to the district of Murragh in the Union of Bandon in Co. Cork.
In the sixteenth century the name was in a transition stage: the earlier Fiants gave as a rule Cogan, Cogane and Coggain, the later ones Gogan and Goggan. Among the Co. Cork place-names in the same source we find Goganrath and Gogganshill, the latter being also given as Knockgogan and a few years earlier as Knockcowgan.
The form Cogan, however, did not become obsolete. Philip Cogan sailed to Spain with del Aquila in 1602; two Cogans and a Coggan were officers in southern regiments of James II's Irish army, Richard Cogan was a "doctor of physic" in Co. Cork in 1707 and in 1798 Pascho Coggin was a witness to a deed relating to Charleville. Charleville, by the way, was formerly known as Rathgoggan - Rathgoggan, indeed, is the name of the civil parish embracing the town of Charleville. Another Philip Cogan (1750-1834), a composer of some note, was also a Cork man.
A very valuable study of the various families of Cogan has been made by Mr. Dermot Murphy, which was presented at University College, Cork, in 1957 as a thesis.
In addition to the Cogans of Norman origin there is a sept of the Ui Maine whose name is sometimes anglicized as Cogan, though Coogan is more usual and nearer the Gaelic-Irish form Ó Cuagáin. They are of the same stock as the O'Maddens.
The small sept of Mac Cogain (the Book of Fenagh and the Topographical Poem spelled it Mac Cagadhain), who were located in Glanfarne on the shore of Lough Allen in Co. Leitrim, dropped the prefix Mac in the eighteenth century and became Cogan and Coggan.
Neither of these, however, is at all numerous today. The variant Cogavin is also rare.
Matheson's Synonymes, published in 1901, mentions Cogan and Keogan as synonymous in Co. Cavan; and in a Co. Meath will of 1834 the testator described as Cogan alias Keogan. Keogan, however, is properly quite a different name from those considered above. Woulfe, mentioning that it is Ó Ceogáin in the spoken Irish language, gives Mac Eochagáin as the correct Irish form of it, which is a variant of the better known Mag Eochagáin (MacGeoghegan).
Link to : Places named "Cogan"
Cogan (The Anglo Norman family of de Cogan, descended from Milo or Myles de Cogan who accompanied Strongbow to Ireland in the twelfth century and was granted lands in county Cork)
Arms: Gules three oak leaves Argent. Crest: A talbot passant proper collared and lined Or. Motto: constans fidei.