MacDyer is the more usual spelling, MacDyre being another variant. It is now mainly associated with Glenties in Co. Donegal though it is found also in the northern parts of Connacht. The first reference to the name I have met is to three MacDyers who obtained “pardons” in Co. Sligo in 1593. I think it is cognate with the well known Donegal name Devir, which, it is true, usually occurs as an O name, but not always: witness, for example, in an inquisition of 1632, a Co. Donegal landowner called Phelim MacDavir a “meere” or native Irishman who, it may be of interest to note, had tenants. MacDuibhir, the Gaelic-Irish form given by Woulfe (who offers no further information on the name), may be accepted as correct. MacDwyer, it would be added, has no connexion with O'Dwyer and is quite distinct from it.

The English occupative surname Dyer appears frequently in mediaeval Irish records as le Deyer etc. but it has no connexion, of course, with the name now under consideration.

*The Patent Rolls of 1373, in a list of leading septs of Thomond and Tipperary, includes the O'Dures. This may be taken as O'Dwyer.

Mac Duibhir Though often written MacDwyer this Donegal name has no connexion with O’Dwyer. Without the prefix Mac, Dyer is mainly found in Cos. Sligo and Roscommon. SIF 61