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{{12}}ap- (2) patronymic prefix in Welsh names, earlier map "son," cognate with Gaelic MAC (Cf. mac). Since 17c. merged into surnames (Ap Rhys = Price, Ap Evan = Bevan, etc.).It is said that a Welshman who evidently was not willing to be surpassed in length of pedigree, when making out his genealogical tree, wrote near the middle of his long array of 'aps' -- "about this time Adam was born." ["Origin and Significance of our Names," "The Chautauquan," Oct. 1887-July 1888]
Etymology dictionary. 2014.