Irish: in County Donegal this is an Anglicized form of Gaelic Mac an Deagánaigh ‘son of the deacon’ (see Deacon); in County Tipperary it can be from Gaelic Ó Déaghain ‘descendant of the deacon’. In other cases the surname is of English origin (see Dean 1).
English: variant of Dean 1.
Dean English: topographic name from Middle English dene ‘valley’ (Old English denu), or a habitational name from any of several places in various parts of England named Dean, Deane, or Deen from this word. In Scotland this is a habitational name from Den in Aberdeenshire or Dean in Ayrshire. English: occupational name for the servant of a dean or nickname for someone thought to resemble a dean. A dean was an ecclesiastical official who was the head of a chapter of canons in a cathedral. The Middle English word deen is a borrowing of Old French d(e)ien, from Latin decanus (originally a leader of ten men, from decem ‘ten’), and thus is a cognate of Deacon. Irish: variant of Deane. Italian: occupational name cognate with 2, from Venetian dean ‘dean’, a dialect form of degan, from degano (Italian decano).