Interesting, Wotcha. I never heard the term used over here for islanders, only for immigrants of Balkan origin and a somewhat darker complexion, mostly Turks.
How did the term came into the German language? Maybe in the times when Germany had colonies in the South Pacific (with the South Pacific Cruiser Station in Apia). Names of colonized or subjected people tend to slip down the social ladder and to be used derogatorily.

Wilfried