An Etymological Dictionary of the German Language/Annotated/Grube
Grube, feminine, ‘pit, cavity, quarry, mine, ditch,’ from the equivalent Middle High German gruobe, Old High German gruoba, feminine; compare Gothic grôba, feminine, ‘pit, cavern’ (English groove); allied to graben. Whether Gruft, feminine, ‘cave, hollow, sepulchre,’ is connected with it is questionable; Middle High German gruft, Old High German gruft, might well correspond in form to graben, as the vowels of grübeln prove. But the absence of the word in the other Old Teutonic dialects probably shows that it was borrowed from the Romance cognates, Italian grotta, French grotte, ‘grotto’ (whence also Grotte, in Modern High German only), which are based on early Middle Latin grupta (Greek κρύπτη). —