The name Fox in Ireland is an anglicized form of the Old Gaelic Mac a'tSionnaigh « mac-a-tsionnaigh
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Tadhg O'Caharny (Carney / Kearney), King of Teffia in the 11th century was called Sionnach (The Fox), the family subsequently where know by the surname Fox.
michael fox mac a tsionnaigh
michaelfox.ie