The surname Gannon, derived from the Gaelic Mag Fhionnáin, means "descendant of Fionnán" or "son of Finan. " It originates from the personal name Fionnán, a diminutive of Fionn, meaning "white" or "fair. " The name is associated with early Irish saints and has been anglicized from the Gaelic patronymic. Over time, the name has been influenced by various historical and cultural factors, including emigration and the need for phonetic adaptations.
