Artificial intelligent assistant

da da

da da, int. Obs.
  [app. of nursery origin; but the history is unknown.]
  A childish and familiar expression for ‘Good-bye!’; the earlier form of ta-ta.

1681 Otway Soldier's Fort. iii. i, Well, da, da, da..prithee don't be troubled, da, da. 1733 Hampton Court Misc. 10 Wife..Da, Da, Monster [exit laughing]. Husb. Farewel, Tormentor.

Oxford English Dictionary

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