It's a northern thing: East Midlands in particular.
It originates from an abbreviation of "conductor", i.e. on a bus or a train. "Ay up 'duc" is what you would (traditionally) say to the conductor as you got onto the bus / tram / train, and eventually it made its way into the more general vocabulary.
I don't use it personally, unless I'm being facetious...
Edit: It has nothing to do with waterfowl
It originates from an abbreviation of "conductor", i.e. on a bus or a train. "Ay up 'duc" is what you would (traditionally) say to the conductor as you got onto the bus / tram / train, and eventually it made its way into the more general vocabulary.
I don't use it personally, unless I'm being facetious...
Edit: It has nothing to do with waterfowl

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