McDermott
An Irish surname from Mac Diarmada, meaning “son of Diarmaid.”
The #1,151 most common surname in the United States (2010 Census) — about 1 in every 10,114 Americans shares it.
Etymology
McDermott is the anglicized form of the Irish Mac Diarmada, literally “son of Diarmaid.” The personal name Diarmaid is very old in Irish tradition; its deeper meaning is uncertain, though it is often connected with ideas of freedom or without envy in later explanations. The surname therefore began as a clan-name or patronymic identifying descent from a man named Diarmaid.
History
The name is strongly associated with the Irish sept Mac Diarmada, especially in Connacht, where the MacDermotts were historically a notable Gaelic family. Historical English spellings vary widely, including MacDermott, MacDermot, McDermott, and related forms such as Dermody and Diarmid. In Irish sources, the name could also appear with the article as a kind of honorific reference to the family chief.
Origin
Regions
Variant spellings
Fun fact
Older Irish usage sometimes treated the surname with the article as an honorific title for the head of the family, not just as an ordinary surname.
From the historical record
“MacCeallach ; a p.n. See Kell MacDermott. From the Iri: j MacDiarmada ; a p.n. (freeman MacDonald, Macdonnell. Fro the Irish MacDomhnaill ; a p. (great chief)”
— British Family Names: their origin and meaning (2nd ed.)