The comics were only available in Danish for a long time so we mostly took the Danish names, so in Icelandic Donald is Andrés Önd (similar to Anders And).
The nephews are Ripp, Rapp and Rupp (Rip, Rap and Rup in Danish).
Funnily enough there’s a generational gap between people who call Goofy Fedtmule (the Danish name) or Guffi (the Icelandic translation name)!