An Etymological Dictionary of the German Language/Grube
Grube, f., ‘pit, cavity, quarry, mine, ditch,’ from the equiv. MidHG. gruobe, OHG. gruoba, f.; comp. Goth. grôba, f., ‘pit, cavern’ (E. groove); allied to graben. Whether Gruft, f., ‘cave, hollow, sepulchre,’ is connected with it is questionable; MidHG. gruft, OHG. gruft, might well correspond in form to graben, as the vowels of grübeln prove. But the absence of the word in the other OTeut. dialects probably shows that it was borrowed from the Rom. cognates, Ital. grotta, Fr. grotte, ‘grotto’ (whence also Grotte, in ModHG. only), which are based on early MidLat. grupta (Gr. κρύπτη). —