Glennon
An Irish surname, often treated as a form of an old Gaelic name linked to Glen- and Glenn- variants.
The #9,165 most common surname in the United States (2010 Census) — about 1 in every 86,702 Americans shares it.
Etymology
The name is generally connected with Irish Gaelic surnames of the Mac/Lennon type, with historical spellings such as MacGlennan, MacGleenan, and Maglennon appearing in older sources. Those forms point to an original Gaelic family name that was later simplified and anglicized into Glennon. The exact underlying Gaelic wording is not always stated consistently in the older dictionaries, so the derivation is best treated as approximate rather than perfectly certain.
History
The name is found especially in Irish records, with older references placing bearers in Ulster, particularly Antrim and Londonderry. In the 19th and early 20th centuries, scholars recorded several related spellings, showing how the surname shifted between Gaelic and anglicized forms. Glennon remains a recognized Irish surname in Ireland and the Irish diaspora, including the United States.
Origin
Regions
Variant spellings
Fun fact
Older surname collections preserve Glennon beside a small cluster of related Ulster forms, suggesting it was part of a broader local naming pattern rather than a stand-alone spelling from the start.
From the historical record
“Glashan. MAC GLENNON for Mac Lennan,;q.v. MAC GLINCHEY for Mac Linchey (Celt.) = Son of Lynch, q.v.”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)