Substituting "adieu" for "ado" is what linguists call an eggcorn—confusing two words that sound the same, especially when the substitution makes a bit of logical sense.
'Ado' Versus 'Adieu' Answers
1. Before Pierre left, he kissed my cheek and said, “Adieu.”
2. We’re going to see Shakespeare’s play ‘Much Ado About Nothing.’
3. Without further ado, we’re off to see the play.
4. Did you know that “adieu” means “goodbye” in French?
5. Aardvark made much ado about Squiggly losing the fishing poles.
See the related article about eggcorns, spoonerisms, mondegreens, and malapropisms.
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