Keenan, ó Cianáin A Gaelic surname meaning descendant of Cianáin diminutive of Cian meaning ‘ancient, enduring’. A sept of Ulster who were hereditary historians to the Maguires. In 1890 Keenan was principally found in Antrim, Monaghan, Dublin and Down, and the estimated number of bearers was 4,610.
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