Protestant names began to appear in Monaghan over a period of about 50 years, from 1606 to the 1650s. As a result of the Tudor, Stewart and Cromwellian conquests of Ireland, as we know, most of the land in Ireland was taken from the native Irish and given to Protestant planters. Monaghan, however, did not have the heavily organized plantation settlement that Northern Ulster experienced. Consequently, Protestant names are fewer. The pattern of land ownership in the 1606 division of County Monaghan, for instance, divided about 60 per cent of the county between a dozen main Gaelic families (former territorial chiefs/leaders) and several hundred of their followers. The rest of the county was divided among just a few British/English planters. Some of the new landlords were men who purchased estates from the Irish chiefs and then brought in more British settlers -- such as John Burnett of Ballyleck in 1609, who bought land from County Monaghan's famous MacMahons and settled it with his choice of Ulster and British tenants. MadPat theorized correctly that: <<great chunks of land were granted to some and then poorer settlers came over to work for them.>>
The Cromwellian settlements of the early-to-mid-1600s included men who were discharged soldiers (taking land as their pay), as well as planters and followers of the new landholding gentry. So, all sorts of surnames came into County Monaghan with these ex-soldiers and civilians, not just lords' and ladies' names. Still, the 1659 census shows only 434 "English" heads of household living in the county, while 3,649 Irish families were residents of Monaghan. If your ancestors were Protestant, they aren't hard to find in that small a percentage.
There are a number of excellent books and articles describing the changes in land ownership in County Monaghan over the centuries and the arrival of specific Protestant groups, with dates, locations, estate records, surname lists, hearth money rolls, etc. Not only were there new English soldiers, planters and tenants whose names began to appear in County Monaghan records, but the Castleblayney area saw an influx of French Huguenots (one of my ancestral lines in Co. Monaghan was a French Huguenot family -- the Calvins/Colvins). Scots settlers came in at different times, as well. So you'll see several types of Protestant surnames coming into Monaghan records of the Tudor to Cromwellian time period, not just English/British. Keep that in mind as you do your research.
Recommended reading:
The History of the County of Monaghan, by Evelyn Philip Shirley (1879)
History of the County of Monaghan for 200 years: 1660 -1860, by Denis Carolan Rushe (1921)
The Monaghan Story, by Peadar Livingstone (1980)
"The Evolution of Estate Properties in South Ulster, 1600-1900," by Patrick J. Duffy in Common Ground: Essays on the Historical Geography of Ireland (1988)
Landscapes of South Ulster, by Patrick J. Duffy
County Monaghan Sources in the Public Record Office of Northern Ireland (1998)
Also, see the Clogher Record articles index by the Clogher Historical Society, which is on-line. Excellent society and publications. And, they offer overseas as well as UK memberships.
Annie