From Ó Dubhthaigh, ‘dark, black one’ — distinct septs in Monaghan and among the church stewards of Donegal's Raphoe.
Gaelic Origin · Root meaning ‘dark, black’
Duffy comes from dubh (‘dark’ or ‘black’), most likely a physical byname. Unrelated Ó Dubhthaigh septs held ground in Monaghan's Farney and, separately, served as coarbs — hereditary stewards of church lands — around Raphoe in Donegal.
A plain name for a physical trait, carried independently by families with nothing in common but the description that stuck to them both.
Irish form: Ó Dubhthaigh
