Firstly the word “duck” as a term of greeting has nothing at all to do with the winged bird of the same name.
It is said to find its origin in the Saxon word ‘ducas’ which was meant as a term of respect; similar to the Middle English ‘duc’, ‘duk’ which denotes a leader, commander; from which comes the title ‘Duke’ and the Old French word ‘ducheé’ - the territory ruled by a Duke.
From these origins it became a greeting and then a term of endearment. This use of ‘duck’ as a greeting is not restricted to the Potteries; although the use here is very common. It is still used an many parts of what was Mercia. Even though they have very different dialects from the Potteries the greeting is used in the Black Country, in Derbyshire, as far east as Warwickshire and Nottinghamshire. In Yorkshire the main term of greeting is ‘luv’ but in Sheffield, which is close to the Yorkshire – Derbyshire boarder the greeting ‘Ey up mi duck’ can be heard.
In Midsummer Nights Dream Shakespeare uses the phrase ‘O dainty Ducke: O Deere!” as a term of endearment.