Do Darguun or Dhaakani goblins and goblinoids have last names in Eberron?

No. They may use descriptive titles —“Munta the Gray” or “Haruuc Shaarat’kor” (crimson blade). If not, they will usually state tribe or allegiance—“Munta of Gantii Vus,” or “Tuura Dhakaan”.

— Keith Baker (@HellcowKeith) January 11, 2020