Arthur, William (1857) An Etymological Dictionary of Family and Christian Names. New York: Sheldon, Blakeman. Public Domain.
MCNAMARA
As described in historical dictionaries
An Etymological Dictionary of Family and Christian Names (1857)
(origin: Celtic.) From Mac, son, and cu-marra or or con-marra, "the hero of the sea." Con-marra was descended from Cas, King of Thomond, from whom came McConmara, or Macnamara. This family were anciently hereditary lords in the County of Clare.
Surname type: From name of parent
Origin: Celtic
Region of origin: British Isles
Country of origin: Ireland
Religion of origin: Christian
Language of origin: Gaelic