Monroe
An Irish surname usually linked to a place name meaning “moor by the Roe,” though some older writers connected it with a red marsh.
The #617 most common surname in the United States (2010 Census) — about 1 in every 5,600 Americans shares it.
Etymology
The surname Monroe is generally treated as a locational name from Irish Gaelic. The older dictionary evidence points to a place on or near the River Roe, with forms interpreted as meaning something like “mossy place on the Roe” or “mount on the Roe.” Another 19th-century explanation connected it with Gaelic elements for “red morass,” but both traditions are place-based and point to Irish topography rather than a personal nickname.
History
In Irish and Scottish usage, Monroe is commonly grouped with Munro/Munroe and related spellings, which appear in historical records in several forms. The name was carried from Ireland and Scotland into English-speaking countries, where Monroe became the standard anglicized spelling. It is best known in the modern era through American and British bearers of the name, but the surname itself is much older and strongly associated with Gaelic-speaking regions.
Origin
Regions
Variant spellings
Fun fact
Older surname dictionaries disagree on the exact Gaelic phrase behind Monroe, but they consistently treat it as a place-derived name tied to the River Roe.
From the historical record
“MONRO \ (Celt.) Dweller at a Red Morass MONROE J [Gael. »!0i««, a morass + ruadh (rfAimute), red] MONSON I = Manson, q.v. 2 for Monk's Son. MONTAGU 1 (A.-Fr.-Lat.) Bel. to Montaigu Montague] (Normandy) = the Peaked Hill [Fr. mont, Lat. mons, mont-is, a hill”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)