👑House of McDermott Mary Catherine McDermott-Bradley
Great-Grandmother of his Majesty.

History:
The progenitor of the family was Dermot mac Tadhg Mor, 7th King of Moylurg, who reigned from 1124 to 1159. He was a vassal and kinsman of the Ó Conchubhair, Kings of Connacht; their common ancestor was Tadg mac Cathal, King of Connacht from 925 to 956. They were based at McDermott's Castle, Lough Key. Later offshoot septs of the dynasty included the families of MacDermot Roe.

Homeland of The Prince of Coolavin.
'The MacDermot" aka 'The McDermott was Moylurg it ceased to exist as a kingdom in the late 16th century, though the senior line of the MacDermot's continued to live a sometime poverty-stricken and precarious existence despite land confiscations and the oppression of the Penal Laws. During this era, they were popularly accorded the title Prince of Coolavin, Today's Irish surnames are underpinned by a multitude of rich histories. The name McDermott comes from the Irish Gaelic Mac Diarmada, which means "son of Diarmuid," or son of Dermot and belongs to the venerable Irish tradition of patronymic naming.
However another source claims the name came from the Irish diarmaid, which meant "the god of arms."
1 Early Origins of the McDermott family the surname McDermott was first found in County Roscommon (Irish: Ros Comáin) located in central Ireland in the province of Connacht, where the family is believed to have been descended from the Heremon dynasty of Irish Kings and were known as the Princes of Moylurg, or the Kings of Connacht, known as the Clann Mulroona. Specifically, they were descended from Teige, a King of Connacht and his son, Murtogh, Prince of Moylurg. Their ancient territories were in the counties of Roscommon and Galway. They were divided into three septs. One of the septs embraced English rule early and relatively painlessly, the other two suffered at the hands of Strongbow's invasion in the 12th century. Of the other two septs, the more prominent is based in Coolavin, in Sligo. This sept was originally found at Moylurg and controlled a large part of Roscommon. "The MacDermott's were ancient Princes of Moylurg, having their territories in the Barony of Boyle, County Roscommon, and parts of the Parishes of Islandeady, Turlough and Breaffy, in Counties Sligo and Mayo. Their chief fortress "was on an island in Lough Key, near Boyle," and they were hereditary Marshals of Connaught. At the present time Connaught is the province in which the MacDermott's are principally found, and half of the persons of the name in that province belong to County Roscommon. "
2 The head of this branch was one of the few leaders who is still credited as an authentic chieftain by the Genealogical Office of Ireland, conferring the rightful title The MacDermot. Moreover, the chief is also unofficially styled Prince of Coolavin. The third sept held a family seat at Kilronan in the north of Roscommon, and was referred to as MacDermot Roe, from the word ruadh, which means "red."

McDermott migration to the United States
In the 19th century, thousands of Irish left their English-occupied homeland for North America. Like most new world settlers, the Irish initially settled on the eastern shores of the continent but began to move westward with the promise of owning land. The height of this Irish migration came during the Great Potato Famine of the late 1840s. With apparently nothing to lose, Irish people left on ships bound for North America and Australia. Unfortunately, a great many of these passengers lost their lives - the only thing many had left - to disease, starvation, and accidents during the long and dangerous journey. Those who did safely arrive in "the land of opportunities" was often used for the hard labor of building railroads, coal mines, bridges, and canals. The Irish were critical to the quick development of the infrastructure of the United States and Canada. Passenger and immigration lists indicate that members of the McDermott family came to North America quite early:
McDermott Settlers in United States in the 18th Century Angus McDermott, who landed in Maryland in 1716 7 Cornelius McDermott, who arrived in Philadelphia, Pennsylvania in 1746 McDermott Settlers in United States in the 19th Century Hen McDermott, who landed in America in 1806.
Henry McDermott, aged 23, who arrived in New York in 1812.
Thomas McDermott, who arrived in Allegany (Allegheny) County, Pennsylvania in 1816. Edward McDermott, aged 17, who arrived in America in 1822.
Roddy McDermott, who landed in Allegany (Allegheny) County, Pennsylvania in 1823.

The McDermott Motto:
The motto was originally a war cry or slogan. Mottoes first began to be shown with arms in the 14th and 15th centuries but were not in general use until the 17th century. Thus, the oldest coats of arms generally do not include a motto. Mottoes seldom form part of the grant of arms: Under most heraldic authorities, a motto is an optional component of the coat of arms and can be added to or changed at will; many families have chosen not to display a motto.
Motto: Honor probataque virtus
Motto Translation: Honor and approved valor.

Variants Variations of the name include:
McDermott, MacDermott MacDiarmada, MacDiarmada MacDermot Roe, MacDermott Roe McDermitt McDermett McDiarmid, MacDiarmid, Irish and Scottish language variants ultimately from Irish McDormand, MacDormand Kermode, Manx language variant [2] Kermit, variant of Kermode and others.

Citations
O'Hart, John, Irish Pedigrees 5th Edition in 2 Volumes.
Baltimore: Genealogical Publishing Company, 1976. Print. (ISBN 0-8063-0737-4) Matheson, Robert E., Special Report on Surnames in Ireland with Notes as to Numeric Strength, Derivation, Ethnology, and Distribution.
Dublin: Alexander Thom & Co., 1894. Print "What are the 5,000 Most Common Last Names in the U.S.?". NameCensus.com, https://namecensus.com/last-names/ "Most Common Last Names in Australia." Forebears, https://forebears.io/australia/surnames "Most Common Last Names in New Zealand." Forebears, https://forebears.io/new-zealand/surnames "UK surname ranking." UK Surname map, https://www.surnamemap.eu/unitedkingdom/surnames_ranking.php?p=10 Filby, P. William, Meyer, Mary K., Passenger and immigration lists index: a guide to published arrival records of about 500,000 passengers who came to the United States and Canada in the seventeenth, eighteenth, and nineteenth centuries. 1982-1985 Cumulated Supplements in Four Volumes Detroit, Mich.: Gale Research Co., 1985, Print (ISBN 0-8103-1795-8) Convict Records Voyages to Australia (Retrieved 27th October 2020). Retrieved from https://convictrecords.com.au/ships/Boyd Convict Records of Australia (Retrieved 2nd January 2021, retrieved from https://convictrecords.com.au/ships/catherine Convict Records Voyages to Australia (Retrieved 3rd March 2022). Retrieved from https://convictrecords.com.au/ships/elizabeth Convict Records Voyages to Australia (Retrieved 28th January 2020). Retrieved from https://convictrecords.com.au/ships/asia/1835 Convict Records Australia. Retrieved on 18th March 2022 from https://convictrecords.com.au/ships/elphinstone New Zealand Yesteryears Passenger Lists 1800 to 1900 (Retrieved 26th March 2019). Retrieved from http://www.yesteryears.co.nz/shipping/passlist.html New Zealand Yesteryears Passenger Lists 1800 to 1900 (Retrieved 17th October 2018). Retrieved from http://www.yesteryears.co.nz/shipping/passlist.html HMS Prince of Wales Crew members. (Retrieved 2014, April 9). Retrieved from http://www.forcez-survivors.org.uk/biographies/listprincecrew.html Lusitania Passenger List - The Lusitania Resource. (Retrieved 2014, March 7). Retrieved from http://www.rmslusitania.info/lusitania-passenger-list/ Lusitania Passenger List - The Lusitania Resource. (Retrieved 2014, March 6). Retrieved from http://www.rmslusitania.info/lusitania-passenger-list/ Titanic Passenger List - Titanic Facts. (Retrieved 2016, July 13). Retrieved from http://www.titanicfacts.net/titanic-passenger-list.html