Anglicized form of Gaelic Domhnall. The final -d of the Anglicized form derives partly from misinterpretation by English speakers of the Gaelic pronunciation, and partly from association with Germanic-origin names such as Ronald. This name is strongly associated with clan Macdonald, the clan of the medieval Lords of the Isles, but is now also widely used by families with no Scottish connections.
English (most frequent in northern Ireland): from Middle English fe(i)th ‘belief (especially Christian belief)’, ‘faithfulness’, ‘loyalty’. This may have been a nickname for a trustworthy person, but was more probably bestowed on one who used ‘Faith!’ frequently as a mild oath or exclamation.