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Last name origins & meanings:

  1. English: from Old French dague ‘dagger’ (of uncertain origin), hence a metonymic occupational name for a maker or seller of daggers, or a nickname for someone who carried one. Middle English Dagger is a later development of the same word. The surname was taken to southern Ireland in the 17th century.
  2. Scottish: on the evidence of the early spelling Dog, Black believed this possibly to be a form of Doig.
  3. German: from a personal name based on Old High German tac ‘day’.