Gahan is a surname with several different origins. One origin of the surname is from a reduced form of McGahan, which is in turn an Anglicised form of the Irish language Mac Eacháin, meaning "son of Eachán". Another origin of the name, in Leinster, is from a reduced form of the Irish language Ó Gaoithin, meaning "descendant of Gaoithín". The personal name Gaoithín is a diminutive of gaoth, meaning "wise", or "wind". In Connacht, Ó Gaoithin is sometimes Anglicised as Wynne or Wyndham. Occasionally, the surname Gahan may be an Anglicised form of the Irish language Mac Gaoithín, meaning "son of Gaoithín", although the more common Anglicised form of this Gaelic name is McGeehan in Ulster.
