거북 • (geobuk) (counter 마리)
First attested in the Seokbo sangjeol (釋譜詳節 / 석보상절), 1447, as 거붑 (Yale: kepwup). Compare the *kep in 껍질 (kkeopjil, “skin, bark”), 껍데기 (kkeopdegi, “shell”).